Not trying to disagree with y'all, but if we step back and examine this, it's pretty odd: No coach would make an offer to a pitcher for whom he had no radar gun readings. It's just one data point, but an essential one. But if a parent wants to collect this same information, s/he is getting too involved. Not saying your advice is wrong; but maybe it ought to be?
If I have a conversation with my son about applying to colleges, there is no way I would do so without knowing his SAT/ACT scores and GPA, among other things. Other factors matter, but those numbers are essential info. The same logic ought to hold for having a conversation about where to try to play baseball: Last year as a rising Soph, my son was topping out at 79 mph. This year as a rising Jr, he sits 83-85 and touches 87. Those two velo profiles suggest (to me, anyway) that this summer he could email some schools that last year might not have been interested, and that it might be worth paying for some camps/showcases that wouldn't have made sense for him in 2017. (There are other reasons to track velo, too, of course, but I'll stick with this one here.) Why shouldn't a parent have whatever information s/he can easily collect? Coaches make the decisions, but the process is driven by underage players deciding when and how to "market" themselves to schools. Parents ought to be able to help their kids with that. (And yeah, in the real world the best "help" may be to do nothing--I appreciate the advice here. I just think coaches shouldn't insist on trying to deal with teens who have limited adult assistance.)