Maybe St. John? There are all inclusive eco-resorts and a good chunk of the island is a National Park so nature, hiking, etc. abound.
There are smaller boat Alaska cruises that are more nature activity oriented but they are extremely pricey. I have a relative who is an avid cruiser and she claims that Princess is the best for Alaska. Princess (other lines probably too) also offer sea/land cruises that include a few days at a nature lodge.
Have fun!
You could do a cruise out of NY on Norwegian to Bermuda. The cruise is totally over the top and the ship is huge but the good thing is that you dock in Bermuda on a Wednesday morning and depart around noon on Friday and that is plenty of time to see and do Bermuda. This May/June Bemuda is hosting the Americas Cup so not sure how that will affect cruise itinerary as where the ship docked at Royal Naval Dockyards was right near where stands were to be constructed for the races and where the ships were in the water training.
We took a 7 day cruise on Royal Caribbean and it was our least favorite vacation. During the day, unless at port, we were very ancy. We don’t like laying around pools all day, and when we did we found it actually quite boring to just see water. On the other hand, we can park it all day on the beach. I’m glad I went, and the ship was extraordinary and we did have fun, but on a scale of 1 to 10, I’d give it a 6. We also like to be busy and relax.
My vote would be an all inclusive. Punta Cana or Cancun seem to be a popular place.
Lots of interest in Cuba. Some are land tours, other cruises. If interested, PM me for a travel agent.
How about Orlando, Florida? Disney and Universal. Great fun for all ages.
I would not book a vacation to Cancun too far in advance… Who knows what will happen in the nearest future. Cuba sounds like a safer bet at this point, IMO.
^Well, given the rhetoric, neither might be a safe bet. 
http://www.cnn.com/2016/11/28/politics/cuba-trump-threat/
It’s not white sand beaches, but we just loved San Diego. There is so much to do to keep busy, different areas it was like 4 mini vacations. We stayed on Pacific Beach, lovely are with the beach, wide walks for biking, etc. Wonderful for the beach vacation you are looking for. We ubered everywhere. Downtown is only 15 minutes away…great trolley tours, San Diego Zoo, Little Italy, the port to tour the USS Midway. Another day, go to La Jolla, 10 minutes from Pacific Veavh. Upscale restaurants and lots of shopping. Beautiful and easy you get over as much as you want.
Go to Coronado Island across from downtown SD…or stay there instead…but I liked the central and lowkey beachy vibe of PB. Take a dinner cruise around San Diego bay. There is literally tons to do there and I would go in the summer.
We always think that we need to travel somewhere exotic for it to be fantastic. We’ve been to Mexico several times, Jamaica, Bahamas, Rio de Janeiro and other SA countries, Costa Rica, the cruise, Europe…and they all were fantastic. How surprising it was for us to find out we had as much of a blast in California! The kids loved it and so did we.
I agree with the answer above with regards to Disney World. There is so much to do both during the day as well as at night. You can do it on a large budget or a smaller one. Disney property has very expensive hotels and more reasonable ones. Same goes for restaurants.Whatever you choose remember it might be the last vacation you are able to take with just the 4 of you. Enjoy the moment.
Have fun
Previous poster suggested Niagara Falls… the Falls themselves pretty amazing site. If you choose that, you will want to go to Niagara on the Lake. It is so charming. Not only are there historic War of 1812 forts, there are wineries, you can rent bikes and just ride around the residential areas, Niagara on the Lake is the home for the Shaw Festival and the three theatre venues,there is both fine and casual dining. Also if Canada itself is appealing there isn’t any places more special in North America to my mind than Quebec City. A MontrealQuebec City trip is a great option. You can also add Toronto which is not a far drive from Niagara on the Lake, if I recall, it is less than 2 hours.
Absolutely agree about San Diego! And for the thrill seekers, Disneyland is not too far away. 
Plus, there are other amusement parks within an easy reach.
@doschicos - dang, I thought Cuba was safe as there is some prime real estate to be had for peanuts… Nevermind.
The more I think about it, a SoCal vacation might fit the OP’s criteria.
I’m a seller on Niagara falls. Couple hours tops.