They must start before park opening at least occassionally. I remember seeing a "Minnie's breakfast" sign when we waited in line for entry, like 30 minutes before the park opened. Also they guided people there when we were waiting for rope drop.
We did Minnie's Breakfast for the first time on November 1, and truthfully speaking it was our least favorite of all meals.
I didn't particularly care about the food, most of it was cold anyway.
The character interaction we got was very short, that was if we got some. Pooh completely skipped our table. I pointed this out to the CMs in character handler outfit who were present, was told he'd come back, but he didn't. They were pretty much all just standing around gossipping instead of paying attention to their charges.
Don't get a late seating, characters may leave for the castle ceremony and not come back in time. That's what happened to us with Chip & Dale.
We were told by the CMs they would be back an we'd meet them, but they weren't.
Chip came to our table after I gave an excited squeal when he came back in, I'm guessing he must have either seen or heard me. Dale went to a family's table and then went backstage without even coming near us.
I had been warned by friends who reported bad experiences in September and October, and I must say at least mine was not as bad as theirs were. But still it will make me think twice if I'll go back next year.