When my Mini Schnauzer mix died of old age 5 years ago, I read everything I could get my hands on about dogs, and subscribed to Dog-Fancy magazine. When my daughter was born, my dog had a habit of stepping on her. The vet told me to keep him leashed and with me so that I could keep him from stepping on her. From what I've read, I would suggest the same thing. Keep your dog leashed and attached to you so that you can keep an eye on him at all times, or keep the dog away from the kid when you have to divide your attention.
Terriers are rugged, high energy dogs and are easily excited. They need a lot of exercise. There are books about raising kids and dogs together. I can't think of any titles off hand, but that would be a good start. I would also suggest getting the dog to a trainer, so that he learns how to behave around kids. Your big dog might enjoy going to a trainer, too. Ask your vet for a recommendation.
Also, I would say that the dog needs to learn that he cannot fight for territory with your kids. Dogs do not live in a democracy: they do what their leaders tell them. The "Dog whisperer" got that right. Do not let your dog be the leader. The leader is the one who gets the best spot.
Good luck,
H.