Ok, firstly, thank you, @Letti0! Secondly, that's a brilliant idea for a 3rd listing with both rooms to accommodate larger groups -- I'll have to figure that oneout.
It seems co-hosts have just about as much control as hosts. As a co-host I'm able to change everything on the listing for which my wife is admin. I just can't change my "payment" from the host. We are sharing the bookings and online activity -- whoever gets to a task first goes ahead and does it.
Hmmm, I still wonder if two listings from the same host are as visible as two listings from different hosts given we both end up earning Superhost status.
Thanks again!