THE RAT,
Can't help you with Prime Time, but Chef Mickey's was good for my DS 11th b-day but my all time favorite was at Rose and Crown in Epcot at the UK! Chef Mickey's was fun for the kids but the B-day part was fairly rushed like they do it all the time. Rose and Crown was wonderful, about 6-8 staff members came out, had DS stand up on his seat, and proceeded to announce his b-day and sing to him. They also gave him a personalized certificate signed by a bunch of the staff as a momento. Our waitress, Louise, was absolutely wonderful. BTW, we celebrated his b-day for a couple of days.
I'm sure it will be special wherever you go. Don't forget a birthday button!