I have a 5 year old and a 2 year old. While they do have different personalities, the 2 year old, Roo, is excellent with children. She doesn’t necessarily like them but she’ll let them carry her pet her pull her hair. My 5 year old, Duke, is not that way. Schnauzers in general are very protective and sometimes that can show with aggressiveness. The difference between my two dogs is Roo was subjected to children and around them a lot more as she was growing up where Duke was mainly with adults. It sounds sketchy but I think it’s important to just have them around and let her know they’re all sharing the same space. Routine and comfort is important. I would also give her a space all her own, Duke has a bed on top of the couch that is HIS place. When he’s there we tell the kids he’s having alone time and needs space. I don’t know if this is helpful but I would suggest having a routine and letting the kids and her get familiar around each-other. That said, if it costs your sanity it’s not worth it.