You are fine timewise---and a 3.1 GPA is not the end of the world to say the least
First thing to do is check with the Clearinghouse on their website and make sure the advanced courses your son is taking are on the approved list of Clearinghouse Core classes for your school
One on one instruction is your choice
The key is get him on a strong high profile team and attend a few showcases in the areas where he wants to attend college so that he gets the exposure
Hope that this helps