The children in question were tied up by the Priest, prior to being sexually assaulted by him.

Otherwise, in answer to your question, I'd ask social services for assistance rather than tying up anyone - unless my life depended on it - which is highly unlikely in the instance of a child much smaller than me.

I do know it was a method of restraint much abused by bad patents in the old days. I have older friends who recall being tied to their cots while their parents went out to party for the evening.