Stephanie,
I think that there are so many great ways to go.
You could try a special experience, like
Surfing Lessons at Typhoon Lagoon, or a spa visit.
A nice dinner is a great idea too, and it doesn't have to break the bank. You can go with romance or entertainment, really with lots of great locations, cuisines, and options. And some, on the more expensive side, have entertainment too. For me the best choices for affordable dining with either a romantic or entertaining side to them, here are my choices by park;
Epcot
Restaurant Marrakesh (romantic with a floor show)
Rose and Crown (romantic with great views)
Chefs de France (casual romantic)
Le Cellier (romantic)
San Angel Inn (romantic)
Hollywood Studios
50s Prime Time Cafe (entertaining)
Animal Kingdom
Yak and Yeti (exotic romantic)
I don't really have a favorite in the Magic Kingdom, but could certainly recommend something there too.
I am glad to offer up more advice. Just send me a follow-up question with more info on what you guys like to do, eat, etc!
Have a magical vacation!