Four weeks ago my wife and I did a trip to Xunantunich and cave tubing. We went with "Tuff E Nuff" and they were very good. You will regret not taking the girls (except for maybe the expense
) . It was a full day but not too much. The ruins hike is comfortable and not too strenuous. The tubing is not too fast at all. It'll knock you off your feet, but you don't feel out of control on the tube. You can stand-up nearly half the way. You really cannot steer incorrectly. Your 9-year old will likely be upset if she doesn't get her own tube. This is not whitewater rafting or anything like that. There is one stretch of caves that is completely dark for about 7-10 minutes. The guide will invite you to turn your lights off. Ask your guide before you get in to warn you when this is coming so you can all lock boats to ensure your girls don't feel uncomfortable. The cave formations are the best part of the trip, not the adventure part at all. You'll also enjoy the ride there through small towns. Ask lots of questions, there's a lot of great culture on the Western Highway. We missed doing Lamani which is the premier trip (as the board folks will tell you) -- but you cannot do anything else with that trip. Ahhhh, next time.