Ya, roosters are always a worry around young children, especially toddlers. A lot of us do seem to have survived nasty roosters as kids, where were all the nice roos. Four hens is probably not going to be enough for a roo, since he is a pet, if you decide to keep him and not get more hens you could make a bachelor type set up for him and only let him out with the hens occasionally and when the kids aren't around. If you try to rehome him, your state thread is a good place to post in for local homes https://www.backyardchickens.com/t/270925/find-your-states-thread and the BST forum has a section for animals in need of free rehoming (you can post an ad there after you have 20 posts). Craigslist, your local farm store bulletin board (or some farm stores will actually take birds) and local 4-H type clubs are other places to check if someone wants a flock roo or project bird.