prometrick, my wife and I (we're in our 50s) swam with the dolphins several years ago in Puerto Vallarta. It was, withot a doubt, the most incredible experience of our lives. There were about 10-12 couples in our group. We entered the water and the dolphins began swimming in and around us. We rubbed their tummies, backs, fins etc. for about 20 minutes or so, it was great. Then, they performed a show while we were still in the water. They jumped out of the water within feet of us! Then each couple grabbed a fin and a dolphin swam around the pool at a FANTASTIC speed while we held on. All in all we were in the water with them for 45 minutes to an hour. The staff filmed the entire session and we bought a DVD for about $30 (very professionally done).
I know the experience is expensive but if I had to do it all over again I wouldn't hesitate for one moment. The only concern I would have is your daughters strength. When they pull you around the pool they're swim with a great amount of speed and power and you have to have good arm strength to hold on. Otherwise no problems. Have fun.