Hi Kelly!
That sound's very nice. My first recommendation is making a dining reservation at the
Rose & Crown Pub in the United Kingdom Pavilion inside Epcot.
I suggest making the reservation at least 90 minutes before Illuminations, the nighttime spectacular at Epcot. If you can't make it 90 minutes before Illuminations, then make it earlier and just linger over dinner! When you get to the Rose & Crown, request a patio dining table. You can not request it ahead of time and there's no guarantee you will get one. However, if you don't get a table on the patio, you can still walk outside to watch Illuminations.
My second recommendation is making a dining reservation at the
California Grill on top of the Contemporary Resort outside that Magic Kingdom. The California Grill is a Disney Signature Restaurant and their food is fabulous! I actually think this would be more romantic than the Rose & Crown, but your question asked for a spot at a theme park. While the California Grill is outside the Magic Kingdom, you have an amazing view of Wishes from there. You can request a window by a table or walk out side on their private balcony. The California Grill is one of my favorite restaurants at Walt Disney World and I can't recommend it enough. Like before, I recommend making a reservation at least 90 minutes before the start of Wishes.
Enjoy planning and write back if you have any more questions!