If 8 of you are on one reservation, all will be issued boarding slots near-simultaneously, I presume. I have never experienced this many at once. Just do it 24 hours out within a few seconds of the instant.
You can print BPs at home (either immediately or later if more convenient), or at the airport.
The 9th one for the teenager can safely be done after the other 8, on the same computer. He/she will be a few slots behind you probably, but cannot imagine a problem sitting by you.