The main thing to avoid is accepting a GRFD or Minuteman Scholarship from the Guard, this will take active duty off the table from the start and there won't be a way for him to commission AD when he graduates.
I agree with Infantry_Dad, each state's NG operates differently and it would be very important that your son talks to the ROTC Battalion about all the SMP options before talking to a local recruiter. A local recruiter does not have the knowledge or experience with ROTC, there job is to get the person to enlist, if that's not done properly it could jeopardize any chance of AD when he commissions.
Bottom line....make sure he talks to the ROTC Battalion before he signs anything with a local recruiter.