Hi Amie,
I am so excited for you that you will be able to have a date night while you are on vacation! There are a lot of great restaurants at Walt Disney World for a date night. Let me make some recommendations for you.
One lovely possibility is
California Grill, located high atop Disney's Contemporary Resort. This restaurant features Californian cuisine, and the feel is upscale. From the restaurant, you can watch Wishes Nighttime Spectacular, the fireworks at Magic Kingdom. It is a truly magical experience!
There are also some wonderful restaurants for an adult evening out at Disney's Grand Floridian Resort & Spa.
Narcoossee's features delicious seafood and sits on the water. It also has lovely views of Wishes Nighttime Spectacular.
Citricos is an elegant restaurant located inside the main building at Disney's Grand Floridian Resort & Spa, and features delicious Mediterranean-inspired cuisine. Finally, for the meal of a lifetime, you can consider the amazing
Victoria & Albert's, a five-diamond dining experience.
I suggested these restaurants in particular for you in part because of how you can get to them. If you choose to go to California Grill, you can take a boat directly from Disney's Fort Wilderness to Disney's Contemporary Resort. You can also travel by boat from Disney's Fort Wilderness to Disney's Grand Floridian Resort & Spa, it will however require transferring boats at Magic Kingdom.
Please do let us know if you have any further questions, Amie!