I have done a few of these in the past. The biggest challenge with such classes is the variety of the people you get in your classes. Not all of them are in the same fitness level, so you need to make sure no one falls behind. It will be better if you have another trainer with you to help with those who are slower than the rest of the group and always keep an eye on everyone to avoid any unexpected trouble.
Other than that, it’s a great way of training a group of people and it can be a lot of fun.