What kind of restaurants are you looking for? The typical chains? Or are you looking for something special? Something inside at Disney or Universal? Dinner at a hotel?
Or are you trying to wing it and intend to eat wherever you see an 'open' sign?
I would suggest you make an early decision on this, since times are much different this year, capacity reduced, and other constraints. Check out what is available of the type of dining you might want and maybe call ahead to find out if they will be open that day. Since you are actually traveling on Christmas day, it might be nice to know what you can expect.