Say to dp and in-laws that in order to make the holiday really special it is important that they spend time together. You will be going out for the afternoon to give them quality time. Give them no time to protest. Have your bag and keys ready.
Another idea is offer to go and collect the takeaway and be gone forever. It’s not your fault the queue was several people deep.
Take the children on a nature walk, a very very long one. The fresh air will do you good.
Clean out the car and wash the car for the journey home.
A migraine will buy you a few hours off.
A sick bug will buy you two days of peace. Sound effects needed
Ladies problems will give you a few hours
Long bath?
Long shower every day
Chat to the neighbours, if they are not serial killers invite them in to dilute the in laws
Go out shopping every day for ‘essentials’
Book a spa treatment
Try and go out to eat
Drink copious amounts of wine, this will take the edge off.
It’s only a few days you can do this 


