1. When travelling with children, especially children under 2, remember to pack extra clothes for yourself and them. Then pack some more. Then some more. They will not only get dirty through playing, they will get you dirty, and then just when you think the far too many clothes you packed will just about get you to to the finish line (and you definitely don't have time to dry a load of washing before you go home again), they will poo and/or sick up all over everything. Everything.
2. Also remember that your fond fantasies of having masses of time to knit are just that: fantasies. I'm not going to tell you to pack less knitting, because one must be prepared for all eventualities, including loss of needles or patterns or brainpower, or who knows, even a sudden stretch of knitting time and superpowered fingers. But just remember, and don't plan on using the holidays to meet any particular deadlines.
3. For you, a "good holiday" may require visiting new and interesting places and doing things you couldn't do at home. All the kids want, however, are interesting toys to play with (new is good, but not essential), and doing things they love to do, even if they do them every dang day. You may be excited that your holiday house is 300 years old, but they'll be excited that your hosts have helpfully provided scooters to play with. You may think an animal park located in the ruins of a castle is the most memorable feature of your week, but they will be happiest about going swimming in a perfectly ordinary suburban pool... even one less good than the one at home.
4. Never overlook the entertainment possibilities of public transport. Especially something as excitingly exotic as a floating railway. (Addendum: Never use the ordinary English name if a direct translation of the foreign name is more fun.)
5. Always go to the zoo. Apart from anything else, zoos have playgrounds. (Need I mention? Always, always look for a playground.)
6. Always go to the castle. Obviously.
7. Always remember that you live in Switzerland now. Holidays are awesome, but coming home is never going to be an anticlimax, for any of you. Never. How lucky are you?