Wow - Full Itinerary!
Well for the MD and PA part I can chime in. Also DC a bit...
For Philly, I haven't done/seen the Campus Park/Ride parking myself but sounds good. If you want specific Philly info let me know - it's where I hang my hat.
You'll want to check out the usual sites of Philly like the Constitution Center, Independence Mall, and the Liberty Bell. All three of those are within walking distance of each other. The Bourse is a place to catch a bite right by them. Or, head to Reading Terminal Market is great to grab a bite - and just to wander around the big farmer and others marketplace.
If it's rainy, the University of Penn Museum is a great alternate to check out.
U of P Museum - It's almost like visiting the set of the movie "Night at the Museum - includes a full Sphinx and Mummies - Also I think the shuttle from the Campus Park and Ride will drop you right there.
Not trying to push you away from Philly, but you might like to squeeze in Lancaster area - they have some great stuff for kids to do - great eats, and don't know if the boys are into it - but Strasburg Railroad and the PA Railroad museum are pretty cool there.
For MD - The Inner Harbor (where the Aquarium is located) is nice. I have not been there in ages so can't give more insight
When in Assateague area check out the NASA WALLOPS visitors center.
Cherry Hill RV Park is a great choice. They are building a waterpark there now for families, and the Cafe has some pretty good Crabcakes!
Right in College Park. Taking the Metro to DC is not all that Hard. There is also a smaller Aviation Museum located near the metro station in College Park.
You can search my blog below - we are generally in the PA/MD area.
Any questions - I'll try to help out.
