My sister in law and mother in law are toxic

This isn’t the first time we have had problems with my husbands family. My husbands mother called him last night crying and hyperventilating because we didn’t invite his sister in law and her family to the little pizza/park date with there brother and his family. My husband spent 3 days last week helping his brother and family move into there first home. He was the only family member who actually helped. So his brother gave my husband brand new shoes and clothes and then offered to have us over for pizza and a tour of the house. We went to his house yesterday and he showed me there new home, we enjoyed some pizza, my boys played with his daughter (cousin) and then he told us there was a park right around the corner. My 4 year old asked him if we could all go and he said of course. We were only at the park for about 15 minutes because it was closing. We all had fun and I captured a couple cute videos and pictures. I posted the pictures on my Facebook and thanked them for having us. One hour later my husband gets a phone call from his mom who is hyperventilating and crying that we didn’t invite his sister and her family. My mother in law always favors her daughter and kids and everyone in the family knows this. They have gone on many trips and outings without us all of the time. However if we do anything and I mean anything without my sister in law and her family she goes straight to there mom and then the boys in the family get attacked. I’m tired of being scared to share our life with family and friends on Facebook. We just want our boys to be surrounded by people who care, love and want to spend time around them. I’m not a confrontational person at all but I’m getting sick of this and want to say something. What would you do ? (My apologies for the long post)