2collegewego- Welcome. First, I'd recommend formal lessons both for percussion and piano. The trick is finding the right teachers. Without knowing the availability of local resources, you're best bet is to ask the people you know (school orchestra/band director, friends, neighbors, relatives) for teacher recommendations. If you have one, a local youth orchestra usually has a long list of teachers of current and past student participants. Be prepared to take a sample lesson with a teacher before you sign up. It's pretty standard procedure to do so, as the teaching style, demeanor and personality of the student and teacher has to be compatible.
Also check with regional and local professional orchestras, as many performing musicians are supplementing income by teaching privately. Another source could be your state's music educators association or MENC (Music Educator's National Conference) or MTNA (Music Teachers National Association), both professional music teacher associations. They normally have a section with private teacher by instrument. You should be able to google the websites. The websites also normally have some FAQs on lessons, getting started, types of careers.
If you are in a suburban or urban area, you should have little problem finding a percussion teacher. Piano should not be an issue, there normally are numerous high quality teachers available everywhere. The piano study will help with musicality, sight reading skills, and elementary theory, and will aid him immensely long term.
I would also try and involve him in a local youth orchestra if possible. Interaction with like minded peers often is one of the best ways for him to increase his skill level.
I'm sure others will chime in. I would also recommend you read BassDad's post here
So You Want To Be Music Major - One Family's Experience, particularly the earlier sections. You may not need all the info now, but it will give you a good idea of what the process involves.
Good luck.