You can park at DS in one of the garage all day, but not overnight. Use the buses to go to and from.
There is a lot to do a DS, just cruise around checking everything out lots to see, if you want something to do, Movies, bowling, amphicars or characters in flight. There are 2 putt golf course's and well if you were wanting to spend$$ a bit more spend the day at one of the water parks, they do have a nice changing room with showers, you can cleanup after a day at the water park and head over to DS for dinner.
You can check out fort wilderness for campfire and movies, they have trail rides not sure of the cost.
Check out getting a Landry's card, its 25 dollars but you get a credit for 25, and if its your birthday month they give you another 25, They have lots of restaurants where you can earn points, so this might be worth checking out. EOS also sometimes offers like a free brownie or cookie when you sign up with them, but read the fine print some times the Disney location in left out of the deals.
Stop by Ghirardelli ( at DS) for a free chocolate one per person, they hand them out at the door.
Animal Kingdom lodge and check out the animals, they have a pretty good buffet here.
Watch the fireworks from the poly on the beach, or the Epcot fireworks from the boardwalk.