My DH and I are Annual pass holders and we are lucky enough to go to WDW every few weeks. But, we have to choose between eating in the sit down or signature restaurants each time we go to Disney world and only go about 15 days a year or eat at the counter service restaurant or snacks and go to Disney world 30 or more days a year. We choose to go 30 or more days and skip the more expensive restaurants. Because of this, we've tried to find special moments in the parks, that are romantic and free!
If I had just one night with my husband in Disney world I would:
~Go to Epcot around 8:00pm and eat dinner all around the world showcase. If you just each get a few items from a few of the different worlds, you can have a filling dinner. Depending on what you get it can be a relatively inexpensive dinner, especially if you share and skip the alcohol. I'd then watch Illuminations from France in the WS while we eat a delicious dessert we got from Les Halles Boulangerie Patisserie. The world showcase gets empty pretty quick after Illuminations, so you can walk slowly "around the world" together as you leave the WS. It's definitely romantic. Even if you don't eat dinner, it's still romantic.
~I would then go to MK to end the night. Depending on what time you get there, watch Wishes and Celebrate the Magic.
~I would be sure to stay until the park closed and then wait for "The Kiss Goodnight." After TKG, we would take our time leaving the park. We love to just walk around MK for about 30 minutes after it closes. IMO, this is the most romantic time to be in MK!