First and foremost, it's a family vacation. So, you'll want to make sure you plan enough fun things to keep your entire family entertained and happy during the trip. You may be worried about the race, but the rest of your family shouldn't be.
My running actually looked a lot like walking to those who saw me struggle down the road during the first few months. However, the thing that helped me get on track was having a plan and sticking to it.
I eased off the pace. Got my breathing back under control. And the epiphany struck: I don't need to run at any particular pace or register any particular time. All I need to do is run at the speed of fun.