D.J.
Hi T., I have been traveling with my 4.5 years old since he was 6 month. Yes, I did always over packed and never sorry about it. To enjoy your Holiday you will need everything you use on daily bases. Your little guy will sense all the changes and that might change a lot for you and him. If you use a stroller, take it. If you are going to use a crib there I would take his sheets, blankets and etc. They can sense the difference in the smell. He will need his toys, too. Try to keep everything as close as possible to his daily routines - feeding and sleeping times, what he sees, what he smells and etc. Also, remember, the adjustment time even for 1 hour change (like the day-light change) takes about 2 weeks, so do not "work" on that. If you are happy and calm there will be no changes in your milk supplies, if you worry, there might be some difference but not too big. Good luck!