Basically agree with Diane. I think the Coppola place, La Lancha, is pretty amazing and not that expensive compared with his two places in Belize. Excellent food, and the rooms even have air-conditioning (unlike Turtle Inn and Blancaneaux). The only downside is that there are a lot of steps to climb if you have any mobility issues. The little town of Flores is charming, too, at the end of a causeway in the lake, and probably worth at least a night's stay, but staying at the park or at one of the upscale places like La Lancha overlooking the lake are musts.
Hertz has a quality car rental operation at the Flores airport (actually the airport is in Santa Elena). Prices are about half of what you'd pay in Belize, and in Flores you get newer, low-mileage vehicles. Tabarini is also good.
The rules keep changing at Tikal park, but I think to do the sunrise tour at Tikal now you have to stay at one of the three lodges in the park. The lodges are overpriced for what they are -- no a/c, power off for much of the day, not always good service -- but you can't beat the location and the fact that you can get back for a mid-day snooze or swim at the two lodges, Tikal Inn and Jungle Lodge, that have pools. It's really hot and humid at Tikal most of the year.
I love Caracol, but Tikal in my opinion is the most amazing of all the Maya ruins in the region. Wonderful structures, lots of wildlife, but just hot as heck.