Yes, go with either Monumental, first choice, or Arlington. You can find them on the web at the Associated Gun Clubs of Baltimore site. Pretty sure you will have to be a club member for them to participate. The boy will be in good hands and shooting in a very safe environment and taught by experienced instructors. I started as a Junior in 1952 and I still compete today at 75. I am not a member of either club.
I don't believe you have to be a member of Monumental for your kids to participate in their junior program, not sure about Arlington. Both have excellent junior smallbore programs. I know that Monumental juniors shoot every Saturday. They usually shoot indoor air rifle in the winter and smallbore outside during warmer weather. I think the cost is $5 to cover expenses. They provide ammo, excellent quality rifles, equipment and coaching.
Where are you located? If you're in Central Maryland, you may want to consider the Anne Arundel Fish and Game Jr. Rifle Program. They have an active rifle team, shooting in local and regional competitions. The team practices on Sunday mornings. However, they usually stop for the winter at about this time, then re-start when the temps get above 50 degrees (IIRC).
Berwyn Rod & Gun Club has a very active juniors program. You do not have to be a member of BRGC for your kids to participate. There is more information at http://www.berwyn.org. If you need more information or help making contact, PM me, though I will warn you that I have no direct connection with the juniors program.
There is a thread on Youth shooting programs in the Recreational Shooting section that you may want to look at for additional resources and programs: Here is the link: http://www.mdshooters.com/showthread.php?t=177663