We toured with the ship (Paradise) in December/03 and took the tour you are talking about. We thought this tour was the hilight of the entire cruise. We drove thru Belize city and out into the country side. It is quite an education. You will see many of the houses in the country look as if they were abandoned, but the local people save a sum of money, buy the land, and when they save more money they begin construction of a house. It is an ongoing project. They say that they hope to give the grandchildren a home some time. The ruins are very spectacular. You are able to climb to the top of one of the pyramids. It should be taken slowly, but you can do it. I am 74 with a knee replacement and did it. I am also female.
You then ride to the river and board a open boat and travel down the river. Along the way you can see a lot of wildlife. We sat unusual birds, bats crocodile, iguana and howler monkeys. If you are going soon, be sure to take along a sunscreen, hat, and maybe long sleeves. I hope you will enjoy it as much as we did. Hope this helps. Have a great cruise.