The only restaurant with a very good view of Illuminations is Rose & Crown.
Actually Tokyo Dining has some extremely good views of Illuminations. They pipe in the music, dim the lights and if you are at or near a window, its unobstructed. We love this place for the food and service and the views of the World Showcase.
OP, if your trip is end of April, Le Cellier is most likely out and many others will be tough to get into.
My favorites in Epcot thus far are:
Corral Reef: Love the aquarium and we have had some great meals and some good ones, never a bad one. But the atmosphere is a favorite of ours
Tokyo Dining: Our most favorite in Epcot
Marrakesh: Love the food, atmsophere and live music and belly dancing.
Le Cellier: Good value for the money, love the soup and mushroom filet but so tough to get into. In fact we haven't been in a few years, the last time I had an ADR I had to cancel last minute due to dd not feeling well, it nearly killed me!
San Angel Inn. Lots of people don't care for this one but we love it. Probably the best atmosphere in all of Epcot and your kids would love the boats and volcano.