Heya!
First of all~ congrats on nearly reaching your mini-goal!
Celebrating is nice and everything, but if you're there with your family to celebrate your cousin~ then don't think you have to overeat or eat as much as everyone else!
If you have something you can make in the fridge of cupboards- something healthy- and simply eat at the same time as everyone else, then i'd probably suggest that.
But if you have to order out; go for soups, salad-dishes without dressing, lean chicken ^.^