Please don't let anxiety spoil your enjoyment of what should be a special time with family/friends/loved ones. That can include enjoying good / new / different foods as well.
With perspective of time a temporary gain really isn't significant, mostly a quick gain is water related and if you do add some fat too then none of us has forgotten how to lose weight.
My numbers were spectacular in gaining 10lbs in 10 days but I had an extra factor in the form of a back injury which restricted my exercise and caused a very swollen back.
The usual temporary gain factors are salty food, more alcohol, air travel, greater volume of food in your system etc etc.
My guess is I gained 7 or 8lbs of water and 2 or 3lbs of fat. Fast forward two weeks and I'm back to goal weight but still got memories of a lovely break and my sun tan.