Just a few thoughts and recollections:
I think planning for 60 and being prepared for 70 would be prudent for a Western Shindig.
I do like the events with at least one common meal, NAFO, EOM, Reuben Run, Black Hills Roundup, Red Lodge Rendezvous, YFO, to name a few.
Turk's SFO is in a league of its own when it comes to meals!
I was surprised at how many bought breakfast from the local Burrito Vendor at the Red Lodge Rendezvous when there was no hotel provided slop.
Check with your local service clubs to find an impromptu meal caterer.
If I weren't doing the North to Alaska Run in 2019 I'd find a venue and start organizing but I'm going North! I'll be glad to consult with anyone that wants to take organizing the Western shindig on in 2019.