Save your money, especially at that age. If you have even decent athletic ability, you can do a better job of training your kid. The key is taking the time. For the price of an hour with a trainer you can buy two good skill buiding DVD's. There a endless free videos on You Tube, etc. Put the money into a bucket of balls, some cones and a portable cage.
I learned the hard way that most of these clinics and trainers aren't providing anything I couldn't do myself, and I never played the game. I wouldn't include specialized training for goalies or FOGO's in this, but that can wait until
he is 12 or so.