Okay, I am home again. We did the transatlantic (plus 4 days in Barcelona) with one suitcase each (on the large size, but still queeked by even the European flight restrictions) plus one garmet bag wich had all of our formals in it (yes we took tuxes for DH and DS, two gowns for me and also for DD and even several sports jackets for DS. We LIKE to dress.) This for a family which insists on dressing for dinner every night
It can be done.
Shoes: We usually have 3-4 pair for a long trip. For us girls: nicer leather flip flops that work well with dressier dresses but can also be worn with shorts, sports style sandals (something very comfortable to wear walking, on the beach, to the pool, etc.), tennis shoes (these are the bulkiest so we wear them on the planes) and MAYBE a pair of strappy heels. The boys take sports sandals, tennis shoes and one pair of dressy shoes. (We pack DH's size 13 dressy shoes full of socks and then put them upside down (in plastic bags) above the "shoulders" of the items in the garmnet bag (filling those corners out all the way). Other shoes get crammed in wherever there is space. Pairs do not need to be packed together nor even in the same bag
Also, if you cannot squish a shoe flat it should be filled with socks, ties, something.
Pants: men and boys can usually wear the same pants 2-3 times for the evening before they need laundered. 3 pair is plenty (and one can be worn on the flight). Bring a Tide pen for spot cleaning.
Dress shirts: Again, men and boys can probably wear these twice in the evening between washings. If you have a dressier group, changing the ties can make the look change dramatically without using much of your packing space. Or wear short sleave button downs (even Hawaiian shirts to Parrot Cay) and hten wear them again durign the day later on.
Girls: We tend to wear sundresses and tank tops with capris. Everything is pretty small and light weight and you can fit A LOT in a suitcase.
Tolietries: We don't bring much. A brush, toothbrushes and paste, saline solution and spare contacts/glasses, sunscreen, etc. . But NO SHAMPOO, SOAP, etc. We use what
DCL provides. I also pare down my make-up bag to the minimum. Also, no hair dryer (okay, I don't even own one--my hair is so long and thick it takes for ever to dry it so I never bother
)
Jackets: One cardigan or sweater for us girls which will go allright with everything. Boys tend to wear a sports jacket if they are chilly (generally only in the evening anyway when a jacket looks appropritae)
Pirate Clothes: We just insist on making those fit
Yes, even the foam swords.
Jewlry does not need it's own bulky case or bag. Put individual peices in various pockets and pack as normal. Do not take anythign valuable obviously.