If I want to collect child support from the father of my three children,do they have to come into contact with him?

It depends. You can file for child support and not involve the children. But he can file for visitation.

Child support and visits are two different things, he can file and ask for visitation any time he wants, he can do it now, if he wants, does not have to be a support order in place.

If and when you file for support, the normal result, he will call and threaten to take the kids, call and threaten to get custody and so on. Those will not happen.

He can of course file for visitation and unless he is a threat to the children he can always get visits