New to this. Sorry I didn't see sooner.
I'm a pretty assertive person. My husband's family is pretty bonkers. I realize that is likely why we dated and were engaged before I ever met them. Anyway, I met them 14 years ago around the holidays and we've been married 13 years this past September. We get together between Christmas and New Years. Hubby has 4 brothers (making him 1 of 5 boys). The first three of the five are from one Dad and the last two are from the father who pretty much raised all 5 boys. He's the one husband refers to as Dad. He has very little contact with bio father and I've never met him or hubs step mom. To the best of my knowledge he hasn't seen them at all in the 14+ years we have been together. Occasional emails only.

Anyway, my parents divorced when I was an adult but have always remained cordial and generally would still get together with us kids for the Christmas holidays putting aside their differences. In fact, after years of divorce and occasional dating, they moved back in together a few years back. My mother is extremely hospitable. My husband is retired military so when we lived states away and returned for the holiday for a few days, there was always clean sheets, plenty of sleeping space, tons of food, an impeccably clean house, etc. That's just the way she is. We could come in at 10 PM and she'd be like "I have a pot of chili on the stove and homeade chicken salad and homeade sour dough bread if you want a sandwich." Always plenty of cookies, cereal in the pantry. Would even call me a 4-7 days prior to our arrival and she would be at the grocery and say "what do your kids eat...I want to make sure I have foods your kids like..." That's just my mother. She's exceptional at hospitality and entertaining. I try to do the exact same thing because that is how I was raised and I want people to be comfortable when they come over.

I tell you the aforementioned so that you can be aware that my husband's family is the exact opposite.

Visiting my husbands family is chaos. If you want food, you bring it. Most of the family lives kind of like hoarders. Unnecessary clutter and garbage. Never ever enough sleeping space or food. During the times we visit, since, thankfully, it's really only a few days once a year, they try to pack in a years worth of "fun". The brothers stay up half the night or all night playing games and the women are left with the overtired, hungry, grumpy kids. Frequently there are arguments. There are cases of monster energy drinks etc because everyone wants to pretty much stay up for three days straight. Mother in law is a depressed, chemically imbalanced, medically fragile pot-stirring woman and the holidays really bring it out in her. "No one loves me..."; "I'm so sick..." All kinds of things. The first few years she mostly just told me how awesome her relationship was with my husband's ex wife and how she was a good daughter in law and I would never measure up...blah blah blah. (Really they are both drama queens and feed off each other...which is fine...let them...but don't involve me or my family. Eventually I told my husband I would not tolerate that type of behavior and if it happened again I would not join in on the family gatherings, although he would always be welcome to go. He had a heart to heart with his mother (which always involved tons of tears and irrational behaviors about how he must hate her so much...) but he stood his ground, saying if she continued WE would not be back...it eventually stopped all together.)

Me. I like quiet. I like a private bedroom to cover up and hide in. I get very, very overstimulated very quickly in this kind of setting. After the first year or two, I was so over this type of "fun". Actually, I was over it in the first five minutes of our first visit, but by the end of a visit or two like this, I realized I had to self protect. Sometimes I use the kids as an excuse to make sure I can have all the things we need. For years we have packed air mattresses, blankets, pillows, groceries and food. While we are there, I cook at least a couple meals. Crock pots are your friends. I take a box or two of cereal, snack foods and when we get there I will get milk, lunch meats, bread, etc. The worst part is not being able to go into a room and hide quietly as there is no private space. The kids sleep wherever they fall. There is dog hair everywhere. (Not a dog hater...we have 3 of them...) Generally though, everywhere you sit there is dog hair. The floors as well. These are mostly educated people so I can't understand this kind of atmosphere. I found if I can lower my inhibitions enough to try to relax and not be so uptight, it's not completely awful and I can try to enjoy myself a little bit even. The kids think it's a riot, especially now that they are a little older. It's kind of a bat-**** crazy type of weekend and though I spend every.single.year dreading the coming visit, once we get there, I chill a bit, (Thanks to a glass or three of wine especially), I just leave on my sweat suit, let the kids run rampant, make sure everyone is fed, and try to let the host know that if any way possible, if they can supply a room with a door I can hook up my air mattress, I will be eternally grateful...just so I can have a place to get away from it all. Sometimes it even works.

I have to really talk myself into going every year, but by making sure I have basic needs met for myself and my family...food, drink, sleeping space, comfortable clothing, etc. we can manage. Once a year though...for 2-3 days and not a minute more.

Another trick to avoid confrontation might be to volunteer to work those days! (Darn, it sucks I can't be there...I have to work.) This works wonderfully!!

Your man needs to be able to try to understand your position and attempt to accommodate your feelings and address your concerns. If he doesn't, you need to do so yourself. I'm not so much into the hiding my food kind of thing. I would bring in a disposable pan and a whole turkey and throw it up on the counter and start fixing it and make soup with the leftovers the next day. If father in law is an angry, abusive, alcoholic though...that complicates things. If he just gets his panties in a wad, then who cares. If he hits me, then I am never going back anyway...so another great reason to not visit. Ever.

Good luck.