Oooh yeah, I did the trip to Chitchen Itza. We paid for a tour, big airconditioned bus, took a long time, (they take you through little towns along the way) ... but well worth it! Of course, I want to visit as many pyramids as I can in this lifetime... but they really are impressive.
We got a little tour, then we could walk around on our own. On the way back we stopped at a pretty nice restaurant area that had lunch set up and then you could change clothes and go swim in the 'cenote' - underground lake. It did take all day.
I think you have a good plan of things to do!
You know I am going to try to get every detail out of you when you get back