What would certification amount to?
That is the million dollar question isn't it.
The certification process should be stringent enough to placate the kneejerk naysayers but flexible enough to optimize volunteer over paid staff.
A background check would be required to keep the children safe from predators, and other unsuitable persons.
Familiarity with firearms would be a must.
Perhaps a course in crisis management would be in order.
This list is just a start.