Divorced in laws ruined my son's birthday!!! 😤

So my husband's parents have been divorced for the past 6 years. We didn't have a huge party for our son last year but this year we really had a big one. Anyways my son turned 2 yesterday and we invited the entire family (mines and his) to his birthday party.About a week ago my FIL asked "is SHE coming to the party, hope not... stupid b*tch, can't stand her." And he laughed. My husband told him that she was going to be there and he offered him anything he wanted not to invite her. My FIL is very spiteful and bitter. MIL and I have had issues in the past but have since moved on so I personally saw no reason not to invite her. My husband felt the same, so of course she was invited. That and the fact that my 2 year old adores BOTH of his grandparents regardless of their antics.Fast forward to yesterday, MIL shows up to the party she wants nothing to do with FIL, she gets all huffy and irritated that FIL's mother is there. It started off a mess! So she's pacing around complaining, my FIL and his family are gossiping and about an hour or two in it all boils over. MIL AND FIL are in each other's faces yelling, and cursing, and screaming ABOUT THE PAST!!MIL stormed off and my 2 year old ran behind her screaming (didn't want her to leave). He puts his hands up to be picked up so she picks him up. My FIL yells from across the yard "put my fcking grandson down" MIL screams back at him "he's my fcking grandson too!". I took my son and took him inside. I was so mad I couldn't help but cry. My husband got upset and started yelling and everyone else pretty much left. Not only were my parents there, but a lot of our friends and their kids were there too! They did the same thing when my son was born, they fought so badly IN THE WAITING ROOM that they were both escorted out! I've been sick of it, hubby is too but won't say anything, and I feel like my son is starting to at least feel the tension. How should I handle this? via /r/Parenting http://ift.tt/2oRtC7x