Most the parents I've had come in with their kids have been fine with using gonad shielding, although I guess there's always gonna be some that object to something. As for the kids themselves, can just use shielding as a way to get them involved and keep their attantion ("Now we need you to balance this right there... Really important job!"). As for explaining, just saying "it can be bad for you round there, and we don't need it on the pic"?

Hope that's some help, but every kid/parent is gonna be different!

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