Baby Shower

Who should I invite?  I've been with my husband in total (dating & marriage) 14 years.  Yet, I still feel I hardly know his side of the family.  His mother and I actually had argued when we were engaged because she kept adding more damn people to the wedding list and I put my foot down.  Should I just say whatever and for the baby shower invite these aunts/cousins that I really don't know because they're going to be invited to my sister in law shower?  I have maybe met the people I'm referring to at my sister in law bridal shower that I basically ran so I didn't talk to people in June 2015, her wedding nov 2015, and then will be at her baby shower in Jan 2017.  Thoughts would be greatly appreciated.