Hi Eric!
I can tell you there is definitely one restaurant with an outstanding view of Illuminations:
La Hacienda de San Angel in the Mexico Pavillon. This restaurant was added to Epcot just this past fall and it boasts an incredible view of the Illuminations fireworks. I do recommend making reservations for this restaurant as far in advance as you can. Reservations open 180 days in advance. Be sure to make reservations for 30 to 45 minutes before the time Illuminations is scheduled for, and ask if they have a table with a great view for you! Hopefully you will see a wonderful show!
Another restaurant that has some seating with views of Illuminations is
Rose & Crown in the United Kingdom. Select seats on the outdoor patio do have great views of the show. I do want to note that the number of outdoor seats is limited, so there is a bit of a chance that you may not get a view of the fireworks if you decide to dine here.
If neither of those options appeal to you, a good plan is to enjoy any of the world showcase restaurants prior to Illuminations and then choose a spot along the World Showcase Lagoon to check out the show Often this works out as the easiest way to plan.
Hope this helps! Have a great time!