You could certainly make a whole day of the zoo. It's kind of hilly so you'll want to take your time in the heat anyway. I forget where you said you're staying but Nats Park is near a metro, so you could do that from your hotel. National Harbor has water taxis from Alexandria if you want to take one just for fun...lots of stores and restaurants at the harbor. I love it there, it's about 20-25 min from my house.The entire month of July has been high 90s, into the low 100s and lots of humidity here in So Cal. Humidity is something we're not used to but looks like we should start getting used to it.
Good point about taking the stroller in the house at Mt. Vernon. We'll be bringing our baby carrier along so I'll remember to have it with us there. Is the zoo a full day zoo like other big zoos (i.e. San Diego, L.A. Zoo)? I'd like to visit but not sure we'll have time.
Good to know about the metro. I looked into the boat from Alexandria to the Nat's ballpark and it's $100 (and actually, that's for regular games. Says they charge $30 PP on busy days)!Might be fun but not sure if it's worth the $100. The two times I've gone as an adult we rented a car and found it reasonably easy. I think we maybe spent $20 a day at most to park and just parked in a central location to the activities we were doing. I'll do some more research on the Metro though. But if we get a minivan or SUV that seats 7, it will probably by cheaper to park rather than do the metro for all 7 of us.
You are all convincing me to skip the Holocaust. I think what we may do is do it the day before the All-Star Game. My mom and I will head to the museum and the guys and kids can go hang out and enjoy the All-Star festivities.
. I do know that the Mount Vernon house itself isn't air conditioned, although the visitors center is. Maybe early in the day is your best bet before it's too beastly.I submitted for the White House tour twice and never heard back from our Congress member, and simply am out of time now. The website said 21 days minimum before trip to submit, at this time since I've never heard back, I'm just moving forward.
If your kid is really into presidential history, you might want to visit Lincoln's Cottage: http://www.lincolncottage.org/
It is a little off the beaten path, but I've heard nothing but rave reviews about it. Lincoln used the cottage as a summer retreat during his presidency. They only recently restored it and built a visitor/education center there. Opened in 2008.
I have toured Mt Vernon several times and I am skeptical about allowing 3-4 hours. You start off with a movie. There is usually a line to get into the main house. There are many out buildings to look at-- and they are spread out. (You might even find Mrs Washington talking to her guests in one of themI know everyone says that the museums and Mount Vernon are a full day thing. I think we'll play it by ear. I'm seeing 3-4 hours max per one unless the kids say otherwise. At least for me and the kids. I don't want to burn them out. This isn't a once in a lifetime. They will take this trip in a few years with their 8th grade class as well.
). Did I mention there is a lot of walking!? (There is also quite a change in elevation if you walk down to the dock.)I have toured Mt Vernon several times and I am skeptical about allowing 3-4 hours. You start off with a movie. There is usually a line to get into the main house. There are many out buildings to look at-- and they are spread out. (You might even find Mrs Washington talking to her guests in one of them). Did I mention there is a lot of walking!? (There is also quite a change in elevation if you walk down to the dock.)
Then, there is the museum which is air conditioned. It is very pleasant to visit after walking around Mt Vernon in the heat of the day. There are some really cool state of the art presentations which your children wouldn't want to miss.
Are you flying into/out of Dulles? If you are, and you are planning a trip to the Udvar-Hazi
Museum... it might make sense to visit this museum on your day of departure if you could get a late afternoon/early evening flight home. (Or, visit on your day of arrival if you aren't too exhausted from your red eye flight)
Who knows? But we'll see. Like mentioned in a previous post, this isn't a once in a lifetime trip. We'll make at least another as a family when DD is old enough and kids will do it for 8th grade trip. If we can get 4 1/2 hours out of the kids I'll take it! And possibly head back to the hotel for some down time before maybe heading into the city. And talking to Mrs. Washington was the absolute HIGHLIGHT of my trip when I went with my husband. I was so disappointed when she wasn't there when I took my grandma and great aunt. Fingers crossed she's there this time!
I doubt, though, that we'll be up for an adventure after a red eye. With just my husband and I, sure. But kids will probably need breakfast and a nap 
Yes, that museum is awesome and the food court is adventurous. A couple years ago my birthday was on a weekend and we'd never been to the National Archives so we went. I found it very interesting. The kids, who were then still older than OP's kids, were bored. Even the one who loves history.The National Museum of the American Indian is a VERY underrated and often overlooked Smithsonian museum. It also has by far the best and most interesting food court of all the Smithsonians.
The National Archives is also not to be missed. You can get timed tickets for this in advance or line up day-of.
@jen7233 I'm sorry you didn't get the White House Tour! I think the Capitol Tour is better any how. You'll enjoy that one. Have a BLAST on your trip - come back with a report on how it went if you can!
