I was at Antelope for the first time the last week in April, what a sight!
Here a few hints regarding bookings and photography once your are there:
1) If you have your own car, there is no point going through a tour operator. All you need to do is to drop in the day before or first thing in the morning and to book a photography tour from the 'front desk' (a hut in the desert).
2) Four or five jeeps will leave at the same time, one of them dedicated to the photography tour. The best time for vertical rays is about 11 a.m. Time in Page is very confusing because lake Powell covers both Utah and Arizona and the Navajos keep their own time. So I can't remember if we had a 10 or 11 departure! In any case there is only one photo tour in the morning.
3) The guy running the photo tour is very competent and friendly. He will ensure that you get as little disruption as possible from the other tourists, but it is a tall order. He will also move the group from location to location to hit the rays just at the right time.
4) A robust tripod is mandatory. I went out with a good monopod and frankly wasted a lot of shots. Many exposures require 30 seconds! Interestingly I had a higher proportion of good shots in faster exposures with my pocket G7 (stabilised) than with the SLR + monopod!
5) The environment is EXTREMELY dusty: first because you walk over thin sand/dust and second because, in order to capture rays of light, your guide will throw a handful of dust in the air. A fair proportion of that ends up on/in your camera. Don't even think of changing lenses on the fly... This creates an additional problem for non SLRs: my G7 collected tons of dust each time the lens retracted automatically. This still blocks the camera periodically. No amount of blowing and dusting has got it back to peak condition.
6) If you have a fancy tripod, then set it up above head level. On a 30 second exposure the odds of nobody walking into the frame are very slim indeed. This is a very small and very crowded place.
7) Last but not least: hang on to your kit and hat! The guides seem to take pleasure in driving like maniacs on the sand tracks meaning that you definitely need one hand to hold on to the car. It is also very windy, with one of my fellow passengers losing her hat although it was pinned to her shirt.