Our peanut/tree nut son has had the best experiences here! THe platter of goodies they bring out rivals the buffet (okay, according to the kids we were with, the platter was better than the buffet and they all picked off it, and management brought ds a 2nd platter!).
There were some of the usual packaged goodies, unpackaged and displayed w/fruit, but there were also other options including caramel corn, jelly beans, sorbet, and other baked goods... it was a highlight of the trip each time we did it, because having been "deprived" of most of the best desserts all vacation long, at the dessert party he was able to indulge (and likely over-indulge)... they even offered us a to-go container for the non-perishable leftovers!
However, one thing to note, we did advise them prior to our reservation and i emailed again to confirm that he would have something to enjoy a few days in advance. Sadly, i have also read a poor review of the dessert party from someone with food allergies, ergo YMMV.