I’m very sorry that you are so stressed, but I think that a little perspective and commitment to change can help.  Try to embrace the concept that your in-laws are argumentative because of their own issues that may have absolutely nothing to do with you.  If you can learn to depersonalize their sabotage of your parenting style, it will be less likely to damage your enjoyment of the celebration.

You probably already know that you can’t control or change anyone else’s behaviour except your own.  First, look inside and be honest about your feelings.  Are you holding on to grudges regarding your in-laws?  Are you rigid and blaming?  Holding onto anger and not being able to forgive only hurts you and your family with negativity.  It will be easier for you to try to let go of some of these things if you recognize that people act out because of themselves, not you. Maybe, your in-laws were raised differently or they are anxious about being loved and relevant to your kids or who-knows-what.  Just know that it isn’t about you. 

Now, prepare.  Speak with your husband and your children. Frontload your kids by explaining that Grandma and Grandpa do some things differently than you and Daddy, but that while some rules might be relaxed during your visits, your home rules will always be the ones you expect your kids to abide by after the celebration.  Your children will understand and it’s okay for them to experience adults doing things in different ways.  Even if we occasionally let our hair down, we still need to keep it combed because undoing knots is brutal.  Your kids probably know the basic behaviors you expect of them, but you can restate them at this time if it helps allay your fears. 

Talk to your husband about wanting to try things differently this year since the arguing never works for anyone.  Chances are he will be grateful and amenable to your plan. 

You can frontload your in-laws, too.  Speak to them neutrally ahead of time and try enlisting their “help “regarding how you’d like things to be handled with your children.  If they feel like helpers rather than adversaries, even if they don’t agree with your tactics they may feel more compelled to go along with them. This will also help you diffuse potential arguments that arise at the party because you can calmly refer to your recent discussions. 

You’ve now armed your kids, your husband, and even your in-laws with the information they need to survive the event unscathed. Now, even if things go a bit off the rails during your get-together, you can still rest assured that your family is aware of what is expected when life returns to normal. If you feel empowered as the mom of a strong family unit and learn not to take your in-laws’ dissension personally, you will feel less prone to engage in arguments and maybe, in their absence, everyone will have a chance to feel the joy in the day.  Try to remember that every family has its share of conflict.  Keep your sense of humor and just do your best.  You’ll be a great example for your children and you’ll be doing the healthiest thing for your family and yourself.  I hope that this helps and that you are breathe and enjoy the holiday season.