Actually, St Louis is not a bad idea! I'm not blowing our horn here, but we do have some interesting things to see and do. Plus, there are some magnificent architectures here making for wonderful photo shots.
Old Town St Charles is just west of St Louis. Great place for shopping, eating and several Casinos. Wonderful brick streets and old French colonial buildings. Great for photos.
Wentzeville Mo is 'The Crossroads of America" and features old car club,corvette club,rat rod club functions throughout the summer. Wineries dot old HWY 94 through to Herman. A cool drive along the river with plenty of scenery, eateries and wines.
There is, of course the Arch. The Original A.B.Bush Brewery, Forest Park and the Zoo. Forest park has a lot of Greek architecture left over from the 1904 worlds fair. Great for a "Meet me in St Louis" event photoshoot.
A Crossfire Club event at a Cardinals Ball game might be a cool group function. Accross the river is Alton IL and the Great river road. The lodge at Pere Marquette puts out a fine feed and there are again shops for the gals all along the route. Check out my Gallary for some shots of that scenic trip.
I am assuming that the covergence of 100 or more Crossfires will take more than a single Saturday/Sunday to pull off. That said we should think about a four day event with multiple activities arranged kinda cafeteria style. This would give everyone a chance to taste the pleasures of their own preference as members come and go to meet their personal schedules.
St Louis is beautiful in Spring, summer and fall. But, June and early July can be unbearably hot and humid. Spring is unpredictable here. If the world endures extreme unpredictable climate change, we won't know it here 'cause that is kinda normal, especially in April, May.
Our most stable and comfortable weather is during August through early October. A Burmuda high typicaly parks over the Mississippi, Ohio river valley and we get Hawaii weather. Daily patterns of 60 - 85 degrees and occasional showers.
I would suggest late August early September as a target date, if St Louis is indeed the place you all want to end up.
I think you all are crazy

but, you are all certainly welcome here!
roadster with a stick