One of the concerns that parents have when traveling with children is that they will be exposed to all sorts of new and crazy germs and everyone will get sick thereby ruining the trip. And I'm not saying that will never happen. But there are some things that I have figured out that at least help keep the germs to a minimum.
I'm sure it's a no-brainer at this point but you should always have at least one container of hand sanitizer close by when traveling with kids. You never know what they are going to find to pick up that they think is SUPER interesting and must be shared with you immediately. I knew I had reached a new level when I heard myself say "We don't pick up things from the Metro floor!". The truth is that kids are inquisitive and keeping them from touching everything in sight is an exercise in futility and will put you on the fast track to insanity.
While we are traveling, I keep a small bottle of instant hand sanitizer in whatever purse or backpack I happen to be using that day. I also keep some hand sanitizer wipes in my red basket. In addition to that, we make dedicated bathroom/hand-washing visits frequently, especially if we have been in a children's museum or science museum where there's lots of touching.
It's hard to keep up a healthy diet while we are traveling because it's just not possible to pack every single one of our meals. But I do pack our vitamins and try to make sure that the kids balance out their soda/lemonade intake with water and milk. My kids take a daily multivitamin as well as a vitamin D supplement. We started the extra vitamin D last winter and our frequency of illnesses dropped DRAMATICALLY. Our current favorites are the Whole Foods 365 Chewy Multivitamins and the Rainbow Lite Vitamin D Sunny Gummies. We take the 1000 IU dosage but they also come in 400 IU.
Ha! I know, that's a funny joke...good sleep w/kids...but seriously, you can at least try! We encourage naps/rest time while traveling in the car and we don't deviate too far from our normal bedtimes even when on vacation. We've tried that and it just creates super grumpy kids and grownups. We also try to not cram too many activities in to one day and schedule some down time to recharge our mental batteries.
But even with all these good ideas the bottom line is that you'll be in new places, exposed to new germs and there's a chance someone will pick up some cooties. But we never let that stop us from exploring a new place!