Bad dog! what should i do?

I have a 4yo lab/golden retriever mix. She's gotten extremely territorial over the past 2 years. We had another dog, but she got ill, and we had a baby. Now the dog I have, Daisy, is ignoring the presence of my 18mo little boy and knocking him over. So my husband went to discipline her yesterday for running flat into our son and she BIT my husband. It drew blood! What should we do?? We are afraid she'll hurt our son now... But she is also part of the family and we would be upset to have to put her down... Help