I'd wait and see if its the arm thats scaring them or just her mannerisms, some of those childrens presenters can be kinda psycho.
I doubt the kids are scared at all, or just very few of them at most who would be fine if the parents explained the situation to them. It's probably just an excuse for the parents to justify their own fears of *gasp* having to talk to their kids about disabilities.
Probably, like I said we had similarly disabled pupils in primary and high school so none of us had a problem with it, having grown up with it.