Everyone is saying go for Le Cellier, so I'll give my opinion and say don't waste your time. I didn't find the food all that spectacular and while the decor is interesting, it doesn't scream luxurious to me. But everyone has their own opinion. I won't waste an ADR on Le Cellier again.
I guess you need to define what your grandmother thinks is luxurious. The cuisine? The restaurant decor? Both?
Maybe you are looking for a 1TS that isn't a buffet and is quieter?
Taking a stab in the dark with my list here:
~ Yacht Club Galley. I found their menu a bit limiting, but it was a nicely appointed restaurant
~ Boma - yes, it's a buffet, but the variety is fabulous and the decor is very unique.
~ The Wave - haven't tried it yet, but everything I've seen and read makes it sound on the upscale side
~ Grand Floridian Cafe - Interesting food items (I'm dying to try the Lobster Topped Hamburger) but with kids friendly items as well.
~ Liberty Tree Tavern for LUNCH. Might not be upscale in decor, but the menu is interesting
~ Crystal Palace - another buffet, but the dinner menu has some adult items and that restaurant is quite beautiful.
~ Marrakesh - Very Middle East inside. The menu may be a bit on the exotic side for the kids, but they have the standard kids menu.