Depends on the privacy settings and whether the child is ever allowed to use the page unsupervised.
I am itching to say YANBU.
But I'm thinking that not everyone gets Facebook and all it entails. If the 5 year old's 'friends' are Granny, Grandpa, uncle, Aunt etc., then maybe it's more of a gimmick than actuall active page.
I'm still not overly comfortable with it and it is against the rules.
So I suppose YANBU after all 