We leave to Kauai on Friday with our 2 kids ( 2 1/2 and 12 months old.) We went to Kauai when I was 6 month pregant with my first, then Maui for a wedding when she was 14 months old and I was 4 months pregnant with the second. Here we go again but with 2 plus a group of family that in total has 5 kids under 4 years old.
My thoughs:
Rent a condo/house. It is nice to have a fridge, kitchen, laundry. It is nice to be able to put something together for a meal (cereal for the kids, etc) and have milk in the fridge. In Maui my daugther got the stomach flu, we had to wash alot of stuff and keep Pedaylite (spell?) in the fridge.
Try to eliminate layovers as much as possible and BUY you child a seat on the plane so he/she can sit in the their car seat. I held my daugther once and it was hard. We flew to Portugal with both of them this summer (13 hour flight that we slipt into 2 days) and we did very well.
Kauai is super laid back with little night life. We stayed in the Poipu area last time which was nice and this time will be in Princeville.
It is doable. I bring lots of snack, toys, DVD player and Bendaryl for the plane ride. Once you get through the plane ride the rest is cake as long as you are perpared and do not mess up the kids schedule too much. I try to stick to the same routine as home for meals, naps, etc so they aren't off and cranky.
Good Luck.