I see what your interest are.
If some one is a child they can be forced and easilly manipulated. They should be protected by their parents, society, and the government by lecherous men who ask starnge questions on the internet. Also, I agree that they cannot enter into contracts.
Your question is out of left field and deserves and more negative response, but I chose to answer it respectfully.
But if the children are of minimal legal age, and if their parents approve, as in the case in the cults I was referring to, it is fine by you.