AK - Depending on if you like BBQ or not, the Flame Tree BBQ is never packed when I'm there, and you can eat by the water, watching the wildlife and E:E's construction.
MGM - The Villians-themed store is great. The shakes at 50's Primetime Cafe rock, as does just about all of the food there.
EPCOT - Restaurant Marrakesh is my favorite stop in all of WDW, well really really close to it anyways. The atmosphere inside the Mexico Pavillion is amazing, as is dining at the San Angel Inn. The food isn't the best, but the setting is.
MK - Aloha Isle, home of the Pineapple Float, enough said... The Main Street Bakery can make the parades even more enjoyable. And Adventureland/Frontierland/Mainstreet thrive at night, each just feel completely different in the dark.
When I went to WDW when I was little (5 or 6) all I kept was a few photos. Then I went again when I was in 11 and 13, and discovered how much fun and thrills were there. Now, I'm only 23, but I actually love EVERYTHING that it has to offer. Every trip brings EPCOT closer and closer to my heart, I love you World Showcase.
I just hope you can convert your Fiance quickly, as the sooner it happens, the less you'll have to keep wondering if they having fun. It sucks trying to gauge a persons feelings with every ride/shop/restaurant/attraction, and as soon as their love is confirmed, you can focus on just relaxing and having fun.