We need to know the shape of the room. Can you submit a diagram showing that including doors, windows and built-ins.

I wouldn’t go that route.  If this was just a large living space, then that would work, maybe add a 2nd sub.  However, since you’re using this as a party space, there would presumably be a lot of people in the space at times, with no clear front stage.  People are notorious for disrupting wifi signals, so you would want to wire your speakers, rather than rely on wifi.  I also think an amp(s) with 4-6 ceiling speakers, plus sub or 2, might be a better option.   This might be a good place to use hanging pendant speakers if you don’t need to high ceilings to remain clear.

Please note as well that Sonos is not good as a PA system.   You can’t connect a mic to the aux input and expect to do karaoke or anything like that.

If budget allows, this is  a case where I think it makes sense to have a professional put in a system for you.

Thank you very much for your response - I will contact a professional and have an analysis prepared.

A Sonos Port feeding a professional amplifier designed for driving multiple passive speakers really sounds like the way to go.

Depending on the volume you want to achieve in-ceiling or pendant speakers might not be enough. I’m really old and haven’t worked in the field for many years but Cerwin Vega used to make excellent speaker systems designed to fill large spaces, no doubt there are still folks doing that.

Oh, looks like they still do:  https://cerwinvega.com/