If the ride is labelled a "fun ride" by the event coordinators, then it should be family friendly--especially the shorter distances. I was nervous at my first group ride and considered it a "skills" test. I agree with the advice to hang back. Just like running, people sprint at the beginning trying to get to the front. If you start in the back and take it easy for the first few miles, everyone will calm down. The other advantage of staying to the right, is it is easy to pull off and stop.

PS. Make sure your daughter understand to stop off the side of the right side of road.

Have fun