Food/Drink:

1. Water (at least 1.5L/person)
2. Gatorade in case of dehydration (one 20 oz sport bottle for the 3 of you to split should be fine)
3. Flying coach overseas, I like to freeze a 6" turkey sub so that it defrosts about 2 hours into the flight, so I can eat whenever I get hungry.
4. A Powerbar Harvest or other similar bar for every three hours of travel time

Entertainment:

1. Noise-cancelling headphones. I have Sony NC-20s and love them.
2. A CD player and a few CDs if you really like them. I only take it when I'm travelling alone.
3. A paperback book
4. Magazines that you haven't gotten around to reading yet and don't mind leaving on the plane or giving to other passengers.
5. Travel sightseeing materials for the first two days at your destination

Health/Comfort beyond the normal toiletries and medicines:

1. Baby Wipes
2. Antacid