I like this thread. Nothing wrong with Mustang dads wanting to give their kids the experience as well.
I did alot of research on this before the wifey agreed to my 2011 purchase. I already had a '99, but those seats are much flatter across the back. The '11 has that huge bump in the middle that is a pain. The '99 even fit our Alpha-Omega ok (its a huge seat), but it was obvious the '11 would not at all.
Unfortunately, the best ones to fit are pricey. The Sunshine Kids Radian XTSL is about the narrowest I've seen. This is because the frame is steel/aluminum so it's not as thick overall. It has lots of shoulder room for the kids as well. You could fit 2 of these in the rear seats on an '11, no problem I think. Downside is that its $299 most places.
I want to check out the Graco My Ride 65. It looks like it has a narrow bucket at the bottom and its under $140, but I haven't seen it in person to check fit.