Megs
I reckon you could get 3 seats across the back. It really is quite roomy in there. Plus in ours being the Ti we have a DVD player on board (which would be great to amuse 4 kids!). I guess you might have to see if you can get the crappy dealer on a good day & see if you can try the seats across the back. I know it will be heaps of fiddling, but such a big purchase might be better. We have our DD in a S&S Meridan in the middle & there is still heaps of room for the people sitting on the sides & you can still fold down the two outside seats without moving her seat, so I can't see why the other 2 seats wouldn't fit.
Let me know if you have any questions!