Hi Brad. Welcome to SMF
What do you class as a "LARGE" gathering and where will that gathering be?
If it is at home for, say, 20 people then probably a 22" WSM or Frontier combined with a 22" kettle. If it is to cater at events then you will want something significantly bigger and mobile. At home I use a combination of Weber kettles, bullet smoker, a home made offset and an FEC-120 and I can cater for 70+ easily with that combination.
If you are looking for something specific for catering for the masses then you may want to contact these guys BBQ Mates (http://www.bbqmates.co.uk/). They have been at Grillstock for the past couple of years, they do a wide range of sizes and styles and they are very reasonably priced. They have stand alone garden smokers and also trailer mounted catering units. They also do an impressive line in custom designed smokers. Just to be clear, I am not connected with them in any way but I have chatted with Nerijus, the owner, on a couple of occasions and he has a real passion for making smokers.
Edited by Wade - 8/2/16 at 2:31am