Your options also very likely include canceling and getting a refund.

I would look at what DL wants SEA-FLL or AA wants SEA-MIA and if it's reasonable and they have space, maybe ask AS to refund all 8 of your tickets and book on DL or AA.

While this situation sucks, you have to give AS credit for trying to get ahead of it. I had a similar situation on AA, where AA unseated me in Paid F a few weeks out, I offered to reroute (I was connecting), but they refused, and ended up downgrading me on the day of departure. In the end I was compensated, but it wasn't pretty and cost them dearly.