If I were you, I would book for a little after 10. You'll have plenty to time to eat and see the characters. And you'll have some time before eating to ride a few rides,etc. We went on Friday March 10. We had a PS for 10:10. The park opened at 9. We had a light breakfast at the hotel, did our toontown madness, rode buzz and went to breakfast. It was great!
We had some of the best character interaction ever. We saw Minnie, Pooh, Tigger, Eeyore, Chip, Dale, Hook and the Fairy Godmother. They all spent a good amount of time at our table. Some even sat down for a visit. Minnie and Tigger played with my son's new Buzz gun.