I think the dog will learn the difference between his toys and the kids pretty quickly. Right now he's just testing the boundaries just like any kids learning. Taking the toy away with an no in any order should work. Maybe get a basket for his toys and take him to his basket anytime you take a toy away so that he learns that those are his to chew on. As for the mouthing, he'll probably stop quickly since you don't seem to feed into it (ignoring him is really effective). Since he can't ask you about the rules, he has no choice but to try new things to see what is or isn't allowed. Just like face licking. I hate it and my dogs learned early on not to do it.