The Bandit is a good starter he will be able to grow with it. I don't know about brushless for a 4yr old. Maybe the XL5 would be beter for him. He will grow out of the Bandit at some point. If you can find the B4 rtr with out the brushless look in to that as it will be upgradeable and it and him can grow together.
Just make sure your LHS has parts for what you buy.