I went into panic mode too when I went home over Memorial Day weekend. I am a creature of habit and when my routine is stirred up, I lose focus. So the first thing I did when I got there was buy all the food I would have purchased had I been home. I would make this food for dinner/snacks as opposed to eating what my family had. It was still a little difficult because I associate my family to eating comfort foods like meatloaf, pasta, mac & cheese, etc.
But the feeling of being in control by having my own food in the house was more satisfying to me than eating off plan and having NO control.
Have a great time with your family and don't have too much anxiety over it. You will overcome this hurdle and be a better person for it!
Good luck and have a safe trip!