Yes, you set out both sweet and savory bread toppings. A typical breakfast might be 1 ham and cheese open faced sandwich followed by 1 sugar-sprinkle (hagel) open faced sandwich or sweet pastry, along with coffee/tea/milk. I set everything out and everyone makes their own sandwiches. Lunch is similar, just more sandwiches! Also - breakfast and lunch have full table settings, because the Dutch (at least the older ones) often eat their sandwiches with a knife and fork.
Sweet = jams, coffee cake, savory = meats: ham, prosciutto, other cold cuts. Not 2 course, just keep everything in the fridge. And have lots of bread (ciabatta freezes really well). Yogurt, cheeses etc, great to have on hand.
Do you belong to Costco? They have everything there, lol. Coffee cake too
Costco has good deals on wedges of Dutch gouda! Also croissants, which also freeze well.
I consider yogurt/fruit sweet. So something like that paired with eggs of some sort or a breakfast meat.
Or a cheddar dutch baby with maple syrup or brown sugar bacon as a side/topping.
If you’re group doesn’t seem to be into breakfast foods though (like if they are really NOT going to eat more than coffee/tea and a croissant - then don’t bother with the breakfast/brunch idea. Maybe survey your group casually.
Will your son-in-law’s mom be arriving at your home straight from a trans-Atlantic flight or will she have had some time to get over jet lag? If the former, maybe wait to have the big breakfast until the second or third day.
I second @coralbrook’s suggestion about coffee. On a recent trip I was subject to fat free half and half, almond milk, and black coffee. I was so glad to get home to my own coffee!
If someone is there for a while, find out their preference. It’s a pretty easy fix and they will be very appreciative!
Ask about tea too. Have lots of varieties, just in case.
Personally, I wouldn’t try to replicate the breakfast they have at home. IMO, traveling is about embracing local culture, and that includes food.
Also, especially since their visit is a lengthy one, absent a few special meals and breakfasts for the holiday, I’d personally would want to feel free to grab food and be part of the family rhythm rather than my hosts catering to me and making a fuss out of every meal, especially breakfasts. I’m sure whatever you do will be appreciated. Don’t overthink it or wear yourself out at a busy time of year.
I have a recipe for refrigerator all-bran muffins. They are pretty sweet. You make the batter ahead of time and bake however many you need each morning. It lasts for a week or more in the fridge.
I also like sausage balls for breakfast. You know those made with breakfast sausage, cheese, and bisquick. I have mixed them up and rolled into balls ahead of time, then froze them on a baking sheet before popping into a baggie in the freezer. You can then take out as many or few as you need. They thaw quickly while the oven is preheating.
3 of our guests will be arriving from Holland so jet lag will be an issue. The other 4 of us live in the US. That’s why breakfast needs to be flexible until they get adjusted.
I remember those sausage balls. We used to have them as appraisers but they would be great for breakfast. I can also find vegetarian sausage which makes it a little easier and a good thing for me to make in advance. I would appreciate the refrigerator all-bran muffin recipe.
Everyone has given great ideas for me to develop a plan. Thankss
Here is a breakfast casserole idea. I had it yesterday at a tailgate and it was a hit with everyone. They made several -one with bacon, one with sauteed onions and red/green peppers and another with just cheese added in. They put them on chafing dishes to keep the warm. This worked wonderfully and everyone was happy - and well fed. 
https://www.allrecipes.com/recipe/132372/bacon-egg-and-cheese-strata/
Personally, I would prefer to help myself at breakfast - not a morning person and really require coffee before making conversation. Everyone has given great suggestions for filling fridge with easy to reheat or self-serve items.
I had this Barefoot Contessa granola on hand last time we had overnight guests and it went over very well. Some used it with yoghurt, others with milk. The recipe is easy to tweet, but watch cook time as I thought it browned faster than recipe stated.
https://www.foodnetwork.com/recipes/ina-garten/homemade-granola-recipe-1940344
Also, if people are staying 2 weeks, they might enjoy accompanying you to grocery store. I love to check to grocery stores in other countries!
And if I was staying with a Texan, I be thrilled to chow down on some brisket and tamales.
We had a dozen people at our house one year. Breakfast was the easiest as folks did their own thing. We had a couple of breads, jams, butter, cream cheese. Fruit. Yogurt. Cereal. Juice and coffee and tea. These were available to everyone…every day…and it was a help,yourself thing. Fridge items were in one spot in the fridge. Everything else was put on the counter the night before.
For an added extra, we put out bagels and lox one morning with everything else. One morning we made blueberry pancakes.
But basically it was a continental breakfast.
One dinner that was a big hit…and easy…was a pasta buffet. We made two kinds of pasta (regular and gluten free) and had a bunch of toppings…marinara sauce, meatballs, grilled veggies, cheeses, “veggie” meatballs. Made some garlic bread and a big salad. People topped their pasta with what they could eat.
One thing we did (and yes…I know this is ecologically not sound). We had paper goods and plastic utensils for breakfast and lunch. Folks took what they wanted to eat…and we didn’t have dishes to wash,
We used regular dishes and real utensil for dinner.
Can I made another suggestion??? Since the MIL especially will be there for an extended time (2 weeks) - maybe consider putting a small coffee maker and basket of simple breakfast snacks - bars, wrapped muffins, fresh fruit that doesn’t ripen too fast - in her room? It might be really nice for her to have a little private time in the morning and time to have her morning coffee/tea quietly.
Who knows people’s sleeping habits? Maybe she rises at 5am each day! It would be nice for her to have some options for light nourishment in her room without disturbing or having to interact right away in the morning. It may go unused but nothing lost. 
Here is the recipe for Refrigerator Bran Muffins. It is an old recipe from my aunt. I remember her making them when we would go visit her 50+ years ago.
1-1/2 cups sugar
1/2 cup Crisco shortening
2 eggs
1/2 tsp salt
2-1/2 cups flour
2-1/2 tsp soda
2 cups buttermilk
1 cup boiling water
1 cup 100% bran cereal (Post)
2 cups All-Bran cereal (Kellogg’s)
3/4 cup raisins, optional
Dissolve 100% bran in boiling water. Set aside to cool. Cream sugar and Crisco. Add eggs and blend well. Add dry ingredients alternating with buttermilk. Add All-Bran and mix well. Cover and refrigerate. Do not stir after refrigerating. (I don’t know why.) When ready to cook, spoon into well-greased or paper-lined muffin tin. Bake 20 min at 400.
edited for spelling
This is what I use for the sausage balls:
1 lb Jimmy Dean hot sausage (it’s not really very hot)
10 oz sharp cheddar cheese, shredded by hand (not the bagged stuff, although that would probably be fine)
2 cups Bisquick
Mix all together. Form into marble-size balls (mine are usually a little bigger). Bake on ungreased cookie sheet 15 min at 350.
Thank you!
Two weeks (even one) is too long to feel responsible for all meals. Have foods in the house for breakfasts at whenever people wish to eat. Let people know which contents of the refrigerator and pantry are available and which are off limits for that night’s meal or other purpose. I do not like carb breakfasts and prefer lunch food or leftovers. Find out from your guests shortly after they arrive what their habits are. Then stock up on foods.
Likewise lunches are not formal. Nor are snack times. Suppers/dinners should consist of some family favorites and local cuisine (your Texas meals). This is an excuse to go out to dinner or lunch at various local places you like, including fast food. Around here there are many different ethnic types for fast food and casual dining.
We sometimes have neighbors over for supper. Sometimes Indian food (H’s culture) or other simple foods. Fajitas means having the beans/chicken, veggie mix, chopped toppings and everyone fixes their own. Likewise serving salads with various ingredients to choose from.
Having done a lot of traveling this summer- DC road trip, London and H’s sister I know what it is like to be away from the freedoms of home foods. Some restaurants with most foods of choice at home (in hotel) makes a huge difference. It is difficult to have everyone all eat together. Be flexible, treat them like family. By now your grown children run their own schedules and did so when home from college. Just be prepared to eat what you bought to stock the refrigerator/freezer and pantry for a few weeks after they leave.
I would not experiment with new recipes but rather make those foods for crowds you don’t for just the two of you. Plenty of people to eat the leftovers. btw- Christmas at home growing up was never a big dinner. There was Mass then breakfast (Santa came Christmas eve). The rest of the day was playing with toys and eating when hungry as I recall. Visiting relatives out of town always meant the same meal, sigh. Casual is more fun.
When we have overnight guests, I always set up the coffee pot, leave out mugs and tell the guests that all they need to do is flip the switch to on, if they are up before me. I also ask ahead what type of milk and coffee creamer they use.