For kids that size, upper 60's, low 70's is probably not going to generate many, if any looks as a pitcher, especially in a baseball hotbed like Socal. I assume they are sophs to be? My son was 5'2 and maybe 120 at that time and was upper 70's. His small size actually probably kept him from getting serious looks, even though his velo was good for his age. 6'2, 200+ and throwing upper 60's will do the opposite....they'll see a big kid who has no arm strength and wonder why. A 10-12mph jump in a year is going to take some work...but realistically that's what it's going to take to be taken seriously by the time they are 15/16U. I'd worry as much about a good workout/training regimen as I would a pitching coach...at least for the time being. I don't think a pitching coach can realistically gain you more than 4-5 mph, but not having seen your sons throw if their mechanics are just awful, maybe he can coax a little more. Arm strength is going to be the big factor....again, if it's me, I'd work on that first, then worry about pitching coach this fall/winter.