Moving to Europe, buying a tiny car, have 3 kids to fit into it, YIKES!

We're moving to Romania this summer. We're going to have to lease a new car over there, and it will probably be very small.

I've got a 50", 50lb 8 year old son, a 4 year old, 35lb daughter, and an 18lb 9 month old to seat...

I currently own two Marathons and a Turbobooster...

I need a really narrow setup--what do you all think of RF Marathon next to FF Radian next to a Parkway? Do the Parkway and Radian mesh very well?

Should I take a Triumph with us too in case the Marathon is too wide? How long does a Triumph last rear-facing, generally?

Anyone know of any European carseats I'd be better off with?

How hard is the Radian to install, really? Is this a really bad idea for a car I can't test ahead of time?

I'd love any advice!!!!

Thanks!