Best Car Seat for Overseas Travel

I would go with a Britax Marathon it's heavy but installs in a sinch and is actually very popular in Europe. On Ebay you cam even buy this wheel kit to install specifically to this carseat and you can have your daughter sit in the carseat and the push her because the wheels on the bottom and there is a extendable handle like a stroller sort of would help in the airport. I like the Marathon because you will definately get your money out of it. Goes from 5 to 65 lbs. My daughter will be 5 in a few weeks and still fits with plenty of room.

We just travelled to the UK with our 20 month old and didn't use a car seat. Prior to travelling I asked an employee of the airline that we were travelling with and she said that a car seat is not required.
Obviously it depends on whether you need it for when you get to your destination (we had one waiting for us).
We paid for a seat for our son as it is a long journey to the UK and I honestly don't know whether we would have been better off putting him in a car seat because he was just all over the place, standing up, sitting down etc. It may have helped him to fall asleep I suppose but then he may of got a little frustrated being restrained.
He was quite happy to sit with the lap belt on during take off and landing.
Good Luck, hope this helped, enjoy your trip.
S.

A friend of mine travels to Europe quite a bit and uses a car seat that converts into a stroller.

Unfortunately, she is there now and I can't get ahold of her to find out the make/model which she LOVES- and is also ATA certified, because I am looking into getting one myself, I found a similar one on ebay at:

http://cgi.ebay.com/New-GoGo-Babyz-Kidz-Travelmate-Child-...

Although I don't think it would completely replace a good stroller, after my last experience at the airport, where we went through security for 2 hours, my daughter was running away and having to strap her in th stroller (you're only allowed a small umbrella style) consumed all free hands for carry on bags and the stroller was not strong enough to hang bags on, so just to get through the airport alone, I find the expense WELL worth it- and of course much safer to bring the carseat on flight!
I found another model at: http://www.amazon.com/gp/product/B0006UF43M/002-###-###-#...
( I believe this might be the one she owns) you might be able to find this on ebay for cheaper

With our boys our travel is strictly limited to our automobiles, but...I believe I have seen what you are looking for in the One Step Ahead magazine - they also have a great website (onestepahead.com). I have ordered quite a few things from them. It may be something you'd like to check out in their travel section. Hope this helps. Best of luck in your travels!

I would suggest the Britax Roundabout. It is pretty pricey, but worth the investment. Both of my girls ride in Britax car seats, and we love them. We have traveled with them, and they are fairly light (for a car seat) and are easy to install. They are FAA approved and both my girls sleep well in these comfy car seats too. But the Britax Roundabout would be the one that your aged daughter would need, it is for up to 40lbs. forward facing and 20lbs. rear facing. Good luck!