I'd echo what the others have said-- if you don't have reason to worry yet, don't.
What are your child's goals? Does your child have a goal of attending a HSLAC or Ivy?
Are those goals the same as yours? (Please know that I'm not saying that you aren't permitted to have goals, and understand that I was in your position with an extra-young college matriculant-- your child is not really developmentally an adult-- but at 13-15yo, your child certainly has his/her own ideas about this, and also that s/he will have to live with the results a lot longer and more intimately than YOU will.) Our DD simply refused to apply to any Ivies. Period.
Honestly-- DD at 13-14 had no problems in this process, other than a few glitches when her age was SO young that they weren't sure what they needed in terms of liability, etc.
We didn't mention it beforehand, generally. After all, we didn't NEED "special permission" since she was entering as a regular, high-school-graduate and fully qualified student, and she didn't WANT to be treated like a pet or lab specimen anyway. She WANTED to be Every Applicant, just with her age there as something a little unusual about her.
Does that make sense?
YOU can't be the one driving this process, though-- it has to be your child.
