Thanks for the kind words on other thread. Believe me she is still a work in progress
Definitely, get your son in the continential grip first. He probably won't like at first and will say it feels funny, but you have to make sure he sticks with it.
The above posts are excellent advice. Please remember it is going to take a lot of work, patience and repetition.
The reason we are focusing heavy on serve at a young age is because of its importance. I see some many times during USTA tournaments kids with great groundstrokes lose partly because of a weak poor mechanic serve. IMO I feel that there is such an advantage if you take the time to learn the serve properly and build on that with tactical serve placement.