You will never change the in-laws. You have to accept that. Even if your husband did talk to them, they will be the same, or maybe worse.
MY mother's father, my grandpa, was very much like your MIL. My mom was his work slave all her childhood, sleeping on the couch at night, never had a bed, so she could keep the fire going to keep the house warm. He finally bought a heater for the house a few weeks after my mom got married. She was the work horse for the family, well her and her mother who passed away when I was five, so I do not remember her. She took care of milking to cow and goats, collecting the eggs, feeding everything, helping with all the cooking and canning and bread making and cleaning and clothes washing and sewing the family's clothes...plus washing her dad's car.
Both her older and younger sister had a room with a bed. Her older sister was wicked mean..to my mom, to my siblings and I. She got married at 13 years old, divorced at 14, married at 15, baby at 16, divorced at 17, married at 18, baby at 19, baby at 20. She kept marrying sailor boys she found in Long Beach, going to AZ to get married, all in the early 1950s, definitely not a good thing to do then...but she was wicked, and her dad would let her do what she wanted, even to her detriment. The sailor she married at 18 was a good man, eventually adopted her first son and got her into shape. He said his family would not accept divorce, so she was going to grow up, cook, clean and raise those kids...and he made sure she did. Before that husband came around she lived with her mom and dad when her sailor boys went out to sea. ...which was most of the time. MY mom had to wash their clothes, etc. LOTS of diapers! That last sailor ended his service time, was an auto mechanic and got their own place for them. Made her grow up.
So my mom was still sleeping on the couch, and her sister got a house built for her to live in in the middle of the property. My mom still did not get a bed or room, as she still was the fire tender. Never in her life at her parents house. She became the fire tender at age 4 when her mom was pregnant with child 3. Mom never slept in a bed until she got married.
Her younger sister was spoiled rotten. Never had chores and even as an adult rubbed that in to my mom.
My mom went to college, paying her own way, working at a store, washing jars and helping elderly neighbors can food, anything she could do to get money. And she paid more for the rent to her dad to stay on her couch as she earned more. And she still had chores to do.
Yet her sister and kids paid nothing for the house, even eating with her parents every meal with kids. Her sailor's money was her fun money.
Mom married my dad, got a teaching credential, eventually even a masters in education. Worked as a teacher all my childhood until she retired.
Now, my grandpa was wicked mean to me and my siblings, and parents. At Christmas or whenever we went to his house, my mom's older sister and kids got lots of stuff. We got nothing or very little, one coloring book for the 3 of us to share with 8 crayons. MY step grandma would apologize and say that grandpa would not let her buy us anything else.
The older sister's husband actually made more money than my dad, and their household income, with his overtime was pretty much the same as both of my parents. I learned that as an adult. BUT my parents managed their money much better.
So much for background...This is what my parents did to help my brothers and I cope:
1. When we went to grandpa's house for events like group birthdays or Christmas or Thanksgiving my parents would bring us a 'special toy' (that my wicked cousins could not break easily) that 'would let us have something to do'. They would say those words so that everyone knew it was for us to be occupied. And generally it was a group type of a toy like a wagon we could play with on the sidewalk and that also gave my dad time out from the clan to watch us. And generally it was a very nice toy. That way we did not really care what the cousins got. Depending on the weather there might also be a new game we wanted, then dad played with us so the destructive cousins could not play and wreck it on purpose. And when WE were done or taking a break from the toy like at dinner, the toy went in our locked car trunk
2. We were told that grandpa liked to give the other families things because they did not manage their money as well as us and he thought that they would not have these things if he did not buy the things for them. Grandpa knows that mom and dad work hard to earn money to buy us stuff and that we take care of our toys so they do not need to be replaced so we would always have enough toys with out grandpa buying us stuff. And as we got older we noticed how many of their new toys were trashed by the end on just one day
3. As we got older grandpa tried to make us into the household slaves---every time we came over. Mom and dad would do things like end dinner with, how about all the men clear the table and do the dishes tonight and give the women who cooked a break. Hard for the men--uncles who were not blood to say no, and they were all decent enough to see what was going on.
4. MY uncle that married my mom's older sister last, the good one who stuck around, saw what was going on in the family and often would bring my brothers and I a small thing like a candy bar or certs package or life savers package and give it to us with a comment like, thanks for setting the table and helping with dinner, raking the leaves, cleaning up the goat mess (yes it was saved for us on Christmas), etc., you are good kids. His nice words were always appreciated! My parents always let him know that, so he continued. And he often would volunteer to held us and tell us to play on the rope swing when he did the jobs with my dad
Funny the things you remember from your childhood!
5. We learned to not share events in our lives with that grandpa, only with the step grandma, who was very nice.
Hoping maybe some of these things would help with your kids.