I've sort of become the leader of our local weekly meetup group. I'm not the most advanced player (we have guitar players who have come over to the light side who can play circles around me), but I'm the one with encyclopaedic knowledge of chords, uke history, how a lot of songs sound etc...
We start by tuning up and getting settled in, then go into songs that have no more than 2 or 3 chords. We don't have a set time limit, but after 3-6 of those, we'll move up to 4 and 5 chord songs. Rinse and repeat until a couple of hours later we're playing much trickier songs, some of which we've begun to orchestrate. I rotate between leading songs to sitting alongside beginners and helping them out while the rest of the group plays. Usually in this role I'll be teaching basic chords or encouraging their technique.
The idea is that we can have an absolute beginner arrive, we show them how to tune up, teach them two chords and almost immediately they're playing "You are my sunshine". Then we show them one more chord and they're playing a three chord song. All within 30-45 minutes. We then stress that they don't overdo themselves on the first night and that they can play along as far as they're comfortable. At the same time, we can have someone on their second or third visit playing along more comfortably, and I'll help them out with any chords or techniques they're having trouble with. For intermediate to advanced players, it's a warm up and with some songs it can be a bit of fun.
I've noticed that some of the first beginners I helped are now helping those who started after them, it's filtering downwards, which is positive, but I like to check up on the beginners anyway to make sure they've been advised correctly.
The main suggestion I have is to get a big screen TV or projector and hook up a laptop. Instead of everyone lugging in songbooks, simply have a library of pdf's that can be seen by everyone on the one big display. Have people email you the pdf's they've found, or bring in a usb stick, and build up your repository that way.