There is only one TS restaurant with a significant number of seats with a decent view of the show -- Rose and Crown. However, only 30% of the tables have such a view, and not only is it not possible to reserve those tables specifically, Rose and Crown no longer allows guests to wait for one of those tables to become available (due to problems with that in the past, presumably).
Personally, my recommendation is to have an early dinner at Chefs de France or Le Cellier, and then find a nice place to watch Illuminations, somewhere around the World Showcase Lagoon -- trying to accomplish both dinner and the show together sub-optimized both, unless you're lucky.