As a quick followup (not that it has much value), I saw Serpens response pretty late in the evening, and by the time I booked the following day, my friend had already confirmed. Having read zephyr17 's comment about hassle/extra steps, I'm glad I was able to ticket us together, on the same initial reservation.

As a complete aside, I happened to log in and take a look today, and noticed the price went down a bit. I "changed" the reservation to the new fare, and got a partial refund - which was a nice surprise.