There's also CRT, but if the others are booked CRT may prove even tougher to get. You are right, however. Those are the only TS in MK; there is also the Plaza Restaurant, but I have always considered it a CS spot with table service. The food is good, but there's not much atmosphere to it.
You may want to consider TS locations at some of the nearby resorts, i.e. Ohana, Kona Cafe, Artist Point Whispering Canyon, California Grill, The Wave, Chef Mickey's, Citricos, Narcoosees, etc. All of these are a quick monorail or boat ride away from MK.