Hi KrisJ. I have a couple of packing tips for travelling with kids.
1) Pack each outfit for each kid in a large ziplock bag. I put shorts, T-shirt, underwear & socks in each one, and it made it much easier to get ready in the morning. I could just toss a package to each child (7 & 4 in my case) and jump in the shower while DH went to get breakfast. Once they're empty the bags come in hand for wet bathing suits, postcards, and any number of other things.
2) If any of your children are fearful of loud noises, take along some bandaids, just in case. My 4yo DD absolutely went ballistic when the automatic toilets started flushing while she was still on board, so to speak. After that I stuck a bandaid over each and every electronic eye, and removed it when we'd both finished. It's much, MUCH easier than trying to lean over your child and cover the eye with your hand.
3) Moleskin, moleskin, moleskin. We'd never used moleskin before our last trip and it worked wonders on a few small blisters that started to develop.
4) Bring lots of sunscreen - gargantuan size for the room and smaller size for the backpack.
I started making a list about a month in advance last time. I bought any extra supplies about a week before, but since I don't have a very convenient place in my house to leave partly packed suitcases, I started the actual packing the day before. If you have a list that itemizes each and every thing you plan to take and which suitcase it belongs in, the actual packing is a snap.
Have a good trip!