Don't be shy about booking this tour -- there's plenty of opportunity and they are going to start having two a day. I believe it's at 8:30am and 9:00am. When I called last week and reserved a spot for DH I was told they were taking ressies through the end of the year. Also, if needed, you can cancel up to 48 hrs. in advance with no penalties. Be aware though that they do put the entire charge on your credit card at the time of booking.