Biting should never be excused but dogs don't just bite for no reason.

If she's only aggressive towards children something must have happened at some point that has made her fear children.

You need to slowly work at making her see children are no threat in a controlled enviroment. Have all children give her treats and gently fuss her, don't let children pick her up (for now) and don't let them come at her from behind, small dogs particularly don't like this.

Educate all children that come into contact with her how to treat dogs properly. It can be turned around but it sounds like it might be hard work. There are plenty of people on here who will give you good techniques but it might be an idea to take her to behaviourist as they will be able to assess the situation better than anyone on here who can't actually see the dog.

If you do want to rehome her find a new family for her yourself, please don't send another dog to a rescue centre.