Hey Bill Great name you have there.. My father was Bill and that is also my son's name.
Tropic Air also offers (or at least they did) either a one day trip OR an overnite trip to Tikal (Guatemala). Tikal is wonderful!! I have been there twice already and want to go again. Last time I was there, we actually stayed at the resort right beside the park. It was fabulous, especially hearing the jungle sounds at nite including the howler monkeys.
I have also been on the Altun Ha trip from AC and although the scale is much smaller, it is a great adventure, travelling up the river and along the 'roads' to the site. We stopped at the Maruba Spa / Resort for lunch too. They were all out of the Royal Rat on the lunch menu but we did have the opportunity to taste :p the Viper Rum! Have you been to Chichen Itza in Mexico? Fabulous... So much history at any of the sites.
Four more days and I will be back in Belize for another visit..
Be careful.. Belize and the Mayan Ruins are addictive..