Amy,
Cirque is a fantastic idea! It is a great show, my wife and I loved it!
But as to dinner beforehand, don't think you are tied to dining at Downtown Disney. While the proximity of an area restaurant would be convenient, you need to remember that Downtown Disney is the travel hub for all the resorts. So dining at a resort and then taking a bus here is more convenient than you might think.
I would recommend dining at
Jiko at the Animal Kingdom Lodge or
California Grill at the Contemporary Resort. They are both exceptional for cuisine, and would make an otherwise exceptional evening unforgettable. At the Grand Floridian I like
Narcoossee's.
That is not to say that there are not great restaurants at Downtown Disney.
Bongos is a personal favorite, and I would consider
Raglan Road for a post-show drink with excellent Irish entertainment.
If you would like to tell me your parents food interests, I am glad to offer other recommendations as well. All you need to do is send me a question directly from my bio page, giving me info on their interests/tastes.
I hope they have a magical vacation!