We took the KTTK tour in August. My credit card was billed at the time I made the reservations. Our tour size was about 15. We were supposed to go on the 9:30 tour, but the guides suggested we go with the 9:00 group as it was smaller. I'm not sure what the cap is on the number of guests for the tour.
I believe the resort monorail does begin running early, (if no stop at the MK, you could always walk from the CR) and at the far left entrance there will be CMs with lists of early PS people for Cindy's and tours. We booked that later tour because I wasn't sure how quickly we would get into MK from the CBM at DTD.
The latest tour on our date was at 9:30.
I really enjoyed our guide Rae, and lunch at Columbia Harbor House.
HTH