Rebecca,
Thanks for your question!
So the answer to your question about entering the Magic Kingdom late one evening and using the same pass the next day is unfortunately no. When you enter a park, regardless of the time of day, the system will charge you one of your theme park day passes.
But if you want to do something in the evening without expending that theme park entry pass, there are tons of other activities you could do. When I arrive in Orlando late enough in the day that I don't want to use a pass, here are some of the activities that I enjoy;
Dine at a resort. The Disney Resorts have a magical quality to them. I love to explore their themes, whether I am in the great American west at
Disney's Wilderness Lodge, the African Savannah at
Disney's Animal Kingdom Lodge, or any of the other resorts. To eat at one of their restaurants can extend that experience, and in the case of some dining locales like
'Ohana (at
Disney's Polynesian Village Resort) or
California Grill (at
Disney's Contemporary Resort), you can even get to watch the
Magic Kingdom fireworks if you time your meal right.
Get your souvenir shopping out of the way. Disney Springs has more Disney-themed gear than you can imagine, but also a lot of other shopping that is worth your time. There is also a range of dining options, from amazing counter service burgers at
D-Luxe Burger to Spanish cuisine (I love paella!) at
Jaleo by José Andrés.
Relax at my home-away-from-home. My family loves to get in some pool time, and starting the vacation off with some swimming helps us get in the vacation & relaxation mood. We also choose to go to bed uncharacteristically early so that we are ready for an early morning at the parks the next day.
I hope that these ideas help, and if you have other follow up questions, please feel free to send them my way.
Have a Magical Vacation!