I would say, yes. Certainly, a sexual offence against a child that attracts a sentence of imprisonment, whether custodial or conditional, is a serious offence. The route at which that is prosecuted, summary conviction or indictment, is really irrelevant. It's the facts of the offence and the penalty it attracts that speak for themselves.
Yes, it seems to me that it is a circumstance in which mandatory registration is justified and could be supported as constitutional if it were to be challenged.