You may want to see if there is a Young Marines program near you. Here it is only 2 hours per week & 1 Saturday per month. My 11 year old nephew just joined a few weeks ago and it certainly has made a difference already.
The cost here is $40 registration and $15 per month. It is much cheaper than a bootcamp. It is run by former Marines, and the kids do push-ups if they mess up, just as the real Corp.