This is a challenging issue.  At our organization, we have two tiers of minor volunteers: 1) minors in 7th & 8th grades, which are required to have an adult accompany them to their volunter sessions, and 2) minors under the age of 18 that are in grades 9th - 12th, which do not require an adult to accompany them. The older minors are more autonomous and usually have the ablilty to transport themselves to their volunteer session. Requiring the younger minors to have an adult attend the session solves the issue of having young minors waiting for transportation after the volunteer session ends.

I think the organization you are requesting information for needs to do a self-assessment on the pros and cons of engaging minor volunteers, the impact on staff capacity and program budget, and which ages are appropriate for unaccompanied service. Then they can implement realistic boundaries and policies.  I think it's perfectly appropriate to set expectations for volunteer service and putting in in writing is essential.

I hope this is helpful.