Apart from extraction and processing (which generally you would only do once or twice a year) there is not much else in the way of equipment that is bulky and only needed on an infequent basis that you have not covered in what you have already agreed to purchase. Anything else is going to be something that people need all the time and buy themselves.
I'd possibly be inclined to add a Sublimox and a decent full face mask to your list - OA by sublimation is by far the most effective treatment and if your members have been educated to the benefits a Sublimox is the Rolls Royce of applicators - I'd hire or borrow one if it was available.
In addition I've just bought one of these on Alibaba Express... Took a couple of weeks to arrive but looks exactly like the picture and well made.
https://www.aliexpress.com/i/4001056695656.html
I can't comment personally on how good it is as I have't used it yet but it has some excellent reviews in the USA where it retails for at least $150 ... mine including shipping came in at £37 so for that price it was worth a punt. I've always used a knife or uncapping fork but it takes time compared to the look of this uncapping plane.
There are lots of videos on You Tube - Google Maxant Uncapping Plane