Case scenarios: sex offender, who is required to register for life, is off of parole and about to be released back into the community. (a) The house in which the offender wants to live also has children living there (in this case, it includes his prior victim). Other than notifying CPS about this situation, can you think of anything to prevent this from happening? I thought about endangering a child, but I'm not sure if that fits. (b) Sex offender has a child. Mom drops off child to live with the sex offender father and then vanishes. Again, other than notifying CPS, is there anything we should be doing?

I'm unaware of any statutory prohibitions against registered sex offenders being around, or living with, children. If they are "off paper" by having completed their probation or parole, then I think you may be stuck. (Other than notifying CPS, of course). The sex offender registration laws are designed to give the public notice, but that's as far as they go.