just got back from an 8 day/7 night and I have 4 children... 2 are 9 and 1 is 5 (the 9 yr olds are B/G and the 5 yr old is G)
I packed 1 new shirt/short or shirt per DD for 5 days. For DS he had 1 new shirt plus a total of 4 shorts for the 1st 5 days. On day 6 I did laundry, the girls had on clean clothes for their morning cooking adventure, DS wore jammies for breakfast in our room and then into swimsuit. I washed a huge pile of clothes for our family of 6...3 washing/4 drying(had to dry 1 thru twice)
Then for Day 7 everyone had a new clean shirt and repeat bottom and on Day 8 it was all repeat.
Plus I had an emergency outfit 1 per child, which everyone wore for a change of clothes 1 night for the Neverland Club. I also had an extra tank top for the 5 yr DD for under a costume, which she ended up wearing for 1/2 of our first day cause she got the orginal shirt dirty.
So recap:
DS (9) had 6 shirts 4 shorts 1 pair jammies, 1 extra shirt/short, a few socks and 12 underware (1 for day, 1 for sleeping) and swim trunks and shirt for to/ from pool
DD (9) had 6 shirts 5 shorts/skirts, 1 extra shirt/shorts, a few socks, 12 underware, 1 pair jammies, and swimsuit and cover-up
DD (5) had same as above DD plus 1 extra tank top and emergency in park short & underware (didn't end up using those though)
DD (18 mo) had 6 outfits, plus 2 extra onesie style shirts and shorts, 2 jammies, and a few white onesies, swim suit, swim bottoms and shirt, plus diapers (she wore everything except the white onesies)
Just so you know we had 6 airline seats and 5 checked bags going, 6 coming home.
Hope that helps a bit, obviously this plan only works if you can and plan to do laundry.
Good Luck!