The facts about mutts are these:
Spaniels are happy, friendly, yet can be excitable little dogs. Like many others, if two dogs for example are 'play fighting', there will be loads of barking, snarling and playful nipping at one another without full blown biting.
Compare that then to a dog and a child: the dog will still think that it's okay to nip, bark and be boisterous. It is never a good idea to let any child play with a dog for those reasons.
Dogs deserve respect if they are taken into a family - and all children need to be taught what is and isn't acceptable. The dog cannot actually speak or have an opinion, therefore adults need to make sure that the dog not only knows its place in your pack, but children have to realise what they can and can't do.
It is all too easy to blame a dog when it's only following its instincts. Either respect it or find it a home which will - it is in your interests, your children's, and the dog's to be totally responsible at all times and not to expect your dog to 'know'.
If you truly feel that you cannot trust the dog, then find a good home for it or hand it in to an animal shelter. But before you do, think very hard about the wisdom of having dogs whilst your children are small.