Thanks for all the feedback--we've got a 14 month old and a 1 month old, so I guess the "big" one could be front facing by then, but the little one will need to be rear-facing for a while yet. And, yup, we're planning on a third, although at the moment we're still kind of reeling, so may rein in the pace a bit here. . .
Makes sense re. the wheel arches, thanks for the tips on where to put the rear facing seat. And I'm about 6'0", but fortunately (for this) am mostly torso, so might be able to have the seat kind of far forward.
Depending on my next job start date, we'll do the return trip over about 2-3 weeks, visiting friends and relatives on and out of the way, so it should spread the misery out pretty well.
The last time I drove east from CO I was in a SIIA 109SW wearing flip flops to try to keep the tranny tunnel heat from melting my feet, so this should be ridiculously plush by comparison . . .