First, ask yourself what you want to get out of AAU.
Second, ask yourself whether your child can realistically achieve what his/your goals are.
Finally, find the right team to help you achieve your realistic goals.
For example, if the goal is play high major D1 ball, but your kid is a junior and is the 8th man on his high school team, don't bother trying to play for the Soldiers. Instead find a team that will help develop his skills so he can make it into the starting lineup on his high school team, start or play a major role on the AAU team and plays in college viewing tournaments for a coach who has a network of college coaches in his circle.