At my local swimming pool in the changing rooms there is a section for kids.
Which generally just means lower benches and bigger cubicles for adults to share and assist them.
I've not put enough though into it, but I do think a naked child seen in public by an unknown adult is a slight issue. The difference between a hijab is that a woman is more likely to defend herself and can take steps in order to be safe. Even then you'll have rapes with men who really want to stalk a woman and are intent on raping her.
We're not talking about children running around naked on their own at your local convenience store. A child couldn't defend itself against an adult regardless of clothing (or lack of).
As for kids, they are far more vulnerable to menacing adults. For a better answer, it would be good to look through the datasets and likelihood of children being taken advantages of.
Most sexual assults against both women and children are by men known to them and occur in closed settings.