YAY! Awesome decision! Welcome to Terp Nation!!! While your son may be going to a bigger school than your daughter, I can tell you from experience that boys are FAR easier to pack/prep for college.
We got my son down in one car trip, with 4 passengers in the one car. For my daughter, it took two cars, two passengers in each car, and still didn’t get everything that she wanted…lol…well, at least I can laugh now, but trust that I wasn’t laughing at the time…
My son said the best thing I bought him as a freshman was a small clip-on fan that he attached to the top of his bed. Let me think on other stuff, but just wanted to say congrats on the decision - I have no doubt your son will enjoy Maryland as much as mine did.