Welcome Andrew. Nice to have you here. Are your kids still growing or are they close to done early? 14 year olds throwing high 60's/low 70's is a little behind the pace in terms of being an early prospect, but in some ways I think that is a good thing. Lots of arm injuries in the Baseball world. Tons of arm whip & high velocity, too early & too often can be a recipe for disaster if kids aren't properly prepared, and even sometimes if they are.
the suggestions for finding a good pitching coach is a good one.