We have 2 different experiences on this.
We booked Donalds for the earliest we could get, 8:10 hoping to get a jump on the 9:00 crowds. Either they were running late that day or they were very unorganized. Even though we arrived well before 8:00, we werent taken to the restaurant and seated until probably around 8:20/8:30. Then after we were told we could go to the buffet and started up there, we were yelled at to sit down to see the characters, so we had to sit and wait for them all to arrive before getting our food. Basically we felt totally rushed after that and stressed out as our waiter was constantly yelling at us. In the end, no we had no jump on the crowds.
At CRT we had an 8:15 PS(maybe 8:20). We arrived nice and early, started walking down Main St and were offered a ride by a fire truck. Drove to the Castle, checked in,and were seated in no time. After a leisurely breakfast, and a bathroom break it was still only about 8:55. So yes, we did get a jump on the crowds during that experience. It was wonderful!
Good luck! I hope you have something like our CRT experience and not Donalds.