Don't overthink too much- We don't have anything fancy...In fact, because they are very packable, we use one of those soft sided cooler bags (got mine at Homegoods!). Last year I had it all packed reasonably tight but by no means did I go to great lengths. We had it packed the night before departure and then our flight was cancelled and we drove to another city for a flight out a day late. By the time we arrived in VG the cooler had been in my checked bag something like 60 hours and while things weren't frozen they were still very, very cold. Even the butter.