Good for you! I'm a big proponent of traveling, and the earlier you start with the kids, the easier it will be. We took our twins to Europe for a ski holiday when they were 9 mos. It was a challenge, but I'm really glad I did it. THey are 5 now and we have taken them every year (except when they were 1 1/2, my husband talked me out of it and I regretted it!).
This is what I recommend....
1. Buy them seats (at least 1). We did not. On the way, it was fine, but on the way back we had to hold them and it was miserable. If you can get the bulkhead, that is great, but the flights we have had would not guarantee it. You should check into it though. If you can get one babybed, consider bringing one car seat onboard and put it in the 3rd purchased seat. This way one can sleep in the car seat and one can sleep on the baby bed. They dont' allow them to sleep on the floor, and you'll want to get sleep too. Also, if you don't buy an extra seat, they could end up separating you due to not enough oxygen masks. Which is also difficult.
2. For transporting -- I stopped taking our double stroller with us on trips after the first trip. It is heavy, hard to maneuver and they often won't let you bring it on board, and alot of airports won't let you retrieve it as you get off the airplane. Instead, I bought two umbrella strollers (that reclined at least a little bit). Then I bought the stroller connecters. This way you can stroll them together or separately -- plus you can bring the strollers on board. It gives you more flexibility, and you won't worry about how damaged your stroller is getting b/c it costs you $50 instead of the $500 double stroller.
3. Allow PLENTY of time in the airport. You don't want to have to rush. Take your time going through security etc. Don't let other people fluster you. If you keep your cool, the babies will too. If they cry, they cry. If you feel anxious, they'll only cry longer.
4. Bring tylenol, motrin or whatever you use. Mine got a cold while we were there and they didn't sell the baby version of what we use... they only had suppositories!
5. Bring a portable DVD player with Baby Einstein or whatever they like to watch. It will be invaluable on the plane.
6. Not sure of regulations these days, but I used to bring plenty of snacks and I would bring 4 bottles, so if there wasn't a place to clean the bottles, I had a spare. I put formula powder in the bottles in advance, so all I had to do was add water. I also brought a small size liquid dishwashing soap (again, make sure it can go through security!) I used it to clean the bottles wherever we were.
7. We brought 2 diaper bags. One had food/bottles/toys/ bibs/blankets. The other had extra clothes/diapers/ wipes/rash/medication. This made it easier to divide and conquer diapering and feeding duties with my husband. I always had 3 or 4 brand new toys that they had not seen before to help keep them occupied, though they were often entertained by a foil packet of peanuts. :)
8. For Clothing -- Layering works best. This way if there is a blow out, you are still left with an extra layer (hopefully), plus I packed 1 NIGHTTIME diaper for every 3 hours -- not needed, but just in case. I also packed 1 extra outfit each. Something small and compact - like a cotton feety pj. You can always use the blankie for warmth.
9. I gave a bottle at take off and landing to help with pressure in the ears, but we never had a problem.
10. Packing for the trip -- don't bring formula, food, or diapers. You can buy them, and they only take up space. Just plan to buy them when you arrive.
11. I brought one outfit per day and my kids both spit up and drooled alot, so I brought two bibs per day, burp clothes etc. But we had no laundry options, so you may not need to bring so much.
12. If you don't have a baby bed for them where you are going, consider an oversized cardboard box to pack their clothes in and they can sleep in it too (if they aren't crawling yet). I know that sounds crazy, but we were going to a remote location and it worked very well for us.
13. I don't recommend renting car seats b/c they were always a pain. It was easier to buy the roller bags to put the car seats in. You can loop the handles to the stroller or wear them as a back pack. Plus they're great for stuffing extra things into if you go over your luggage weight on the way home.
I think that's the big stuff, but if you have any other questions please don't hesitate to contact me. Have fun!
I know the first trip was hard getting ready b/c I was afraid I would forget something, but every other trip has gotten easier and easier.
Have Fun!
PS -- I just saw Liz's comment about the front pack -- yes, we brought ours too on that first trip. It came in V. handy when we were changing planes and had to go outside and ride a tram to a small plane. (Not sure if you will have to do that.) But it's a good idea to have them, so your hands are free.