Yeah, I was pretty shocked when I heard about the dinosaurs. It has to be one of the most crowded rooms in all the Smithsonian Institutions. On the plus side, though, I think the Washington Monument might be back open by then. If it is, I'd suggest getting the cheap tickets (like $1.50 each) online to make sure you can get up there. Otherwise, I think you have to get in line at like 4 AM to get a free ticket the day you want to go. Seriously, that's what I've heard. Never done that, but that's pretty much what you used to have to do. Maybe it's different now with the online tickets. Other good views of the city are from the National Cathedral and Old Post Office Pavilion (someday to be a Donald Trump hotel). Each have observation decks. Nothing like the Empire State Building, of course, but pretty good views.
Cheap tickets are also available online for the National Archives (but that's not nearly as difficult to get into as the Washington Monument). Free tickets are needed for the Bureau of Engraving and Printing (see a bunch of money printed) and Holocaust Memorial (if you think your kids are up for something like that).
I'm sure you've done this, but I'd suggest looking around the
Smithsonian site to see what special exhibits are at each museum to help plan your trip.
The National Building Museum is not part of the Smithsonian and is a lesser known spot. It does have an admission for some of the exhibits.
Oh, and there's a Navy ship docked at the Navy Yard (near the Nats stadium) that is free and open to the public. It's called the USS Barry, if you are interested and want to look it up. If you go to a game, probably worth swinging by the Barry and hanging out in Yards Park before the game.
You used to be able to take a canal ride in Georgetown, but they've stopped those and only do them from
Great Falls. I remember doing that during a school field trip and keep meaning to take my kids. Since you'll have a car, swinging by Great Falls either to or from Udvar Hazy might be a good idea. And then hit that restaurant suggested earlier in Tysons Corner. Actually, just remembered those rides are on the Maryland side of the river (Udvar and Tysons Corner are in VA), so not sure if it's worth driving back and forth across the river just for that. You can access views of the falls, though, from either the VA or MD side.