My daughter also ran her first one mile fun run this past year. She was also 5 1/2 at the time. She is now 6. The run was for donate life so it was a perfect 1st run for her. I don't have any answers to your questions but I thought I would share my daughter's experience as well. We plan to do more once the heat isn't so bad. Maybe this Fall sometime. I do feel it is a great exercise for them as long as they pace themselves.
Good luck! Amy
Good luck! Amy