I have to be honest, Chris, I can't imagine being as tall as you and putting kids in the backseat of a Golf/GTI platform car. My GTI is already starting to feel too small. Basically, when I comfortable in the front seat I'm constantly getting kicked in the back by the 4yr old. And there's not much room for stuff either. And no way you're getting 3 kids seats in the back of a Golf either. I've got two in mine and there's maybe a 10" gap between the seats. Given that one of yours will be an infant seat the situation would be even worse.
Don't get me wrong, the GTI is fun to drive. But lately it's been aggravating an old hip injury - the side bolster pushes on a painful spot on my left leg - and I'm giving serious thought to replacing it. It's also (even with full warranty coverage) cost me more to maintain in 18 months than the Camry did in 6 years.
A good friend has a Focus ST and loves it, also has two kids and it's just bigger enough from what I can see so maybe the RS would be the perfect family hoon mobile.