May I offer a suggestion please?
How about adding information cards about how to play the various games on each machine? When I attended the last event I saw people trying to play games, but putting them down seconds later in frustration because they didn't know how to play them. Frogger on the 2600 (I think it was) is a good example, since you set the direction, and then
move, which isn't how games usually work. Also saw people exchanging cartridges on machines which were still powered up, which I always thought wasn't too healthy for them? (the machines that is, and possibly the people seen doing it?!)
What I think would be useful is a card with some simple information about how to use each machine, and a card for each game that is available to be played on it. Hopefully then people will take a little time to learn about how the play the games, respect the hardware, and ultimately have a longer and more enjoyable day.
I appreciate that most people attending probably know how to use most of the hardware on display, and to play the games usually found on them, but for partners / friends / children who don't I think it could really help, and also help prevent any damage to these machines.
On a personal note, maybe somebody could run my ZX81 game VIRUS on a Zeddy this year? Would make my day.