Peter Pan in Fantasyland--always the longest line but worth it for young and old (trust me, i'm old!)
toontown is really fun to walk around--push all the buttons, pull all the doors, etc. and look for the talking manhole cover by the toy store and the talking water fountains by the garage!
Taste Pilots Grill in DCA has very good food--have had breakfast and lunch there.
Breakfast at the river belle terrace in adventureland is always fun as you can sit on the patio and look out over the rivers of america and watch the mark twain go by.
ALSO REMEMBER--DL and DCA are just mere steps from each other with DowntownDisney in the middl--so there is not a lot of travel time between parks and your hotel. you can hop the monorail in the mornings from the DL Hotel which drops you off in tommorrowland right by the matterhorn (DON'T MISS THIS--YOU WON'T FIND THIS ANYWHERE ELSE!)
Another thought--go to the Mark Twain cast member at the entrance and ask if you can ride with the captain! I think you can take a maximum of 4 people but it is great fun--you get to blow the whistle, and "steer the boat"--you also sign the log and get a steamboat pilots license! THIS IS a must do!
But most of all, take some time to sit on Main Street and just watch people and think about how Walt used to walk those same streets every morning in his bathrobe. You will feel his spirit there--it is a very special park!
Also, be sure to dip your hat as you go by Walt's Apartment over the fire house--they always have a light in the window in his honor.
Anymore questions, feel free to PM me--I practically live there!