Having gone through this last year with my son, I have felt the pain (and guilt) you expressed. There are other venues, however.
Contact the schools your son is interested in and see if they hold open tryouts or camps. Jucos and D2's usually hold free, open tryouts. If I remember right, we went to 4 free tryouts and paid for two. One cost $50 and the other cost $135 - but it had 8+ schools there and fewer players.
Start going to every major league tryout you can find near you. They are free, you can go year after year, those scouts know everyone and most allow you to start attending at age 15. Have your sons tell the scouts up front that they are looking for a place to go to school and play ball and have them ask the scouts to pass their info to college coaches. The scouts will pass their info on,
if they think your sons are capable. If the scout likes your boy, he will steer him somewhere he can continue to watch him. Get the scouts names and addresses for references.
If you can afford a good showcase, go. My son was asked at every tryout what showcases he had been to and what his results were. They also asked what summer team he played on and who his coaches were. Not having either of these was a disadvantage; however, he was able to counter this disadvantage by being able to give several pro scouts (from the major league tryouts) as references.
Get ready for some extended road trips and enjoy the time with your sons! It made for a great series of mini-vacations and bonding for my son and me last year
.