I don't know where to start. This is not a daycare center where children are running amok and knitting needles would be used as a weapon. It's a hospital FFS!!! I'm sure that it's not such a fun place that young children are popping in alone to pass the time. Children are probably with at least one responsible adult who could either take the OMG!!! It's a knitting needle from the child or supervise them and instruct them in the proper use of a tool.
And really, if a child were to injure themselves (has this happened or did some over-zealous administrator and/or lawyer miss lunch and stop thinking
Really, what's next? Children fall off chairs all the time. Will the hospital remove all the chairs and put in nice, safe mats for people to sit on.