I'm a huge fan of getting rescued dogs as they all deserve a loving home but please be careful where you get one from especially with children as usually their backgrounds & how they have previously been treated are largely unknown.
Organisations like the RSPCA & Australian Working Dog Rescue are great because they will work with you to find a dog that suits your lifestyle. My friend got one from the working dog rescue & they continued to communicate with her after she had the dog to make sure it was fitting in with her & her little girl. She was also given a trial with the dog first which I'm pretty sure the RSPCA don't do. I thought this was great & they don't want to see their dogs back at the pound etc so they were wonderfully supportive.
Good luck OP, having a dog is so nice for your kids & I hope you can find one that suits your family.