Sounds like a lot of fun. I have an Advantage Arms .22 conversion for my Glock 17, I bet I have shot less than 100 rounds through it since buying it several years ago. This would be a great use for it. (And for the 9mm as well...) Also have a nice High Standard Sport King that I would consider using, but only have one "good" mag for that one.
Saw the videos, and a few questions: for the rimfires; no drawing from holster, extra mags desirable but not required? I do have 4 mags for the Glock conversion.
We've had several people use the .22 conversions for Glocks in the past. (I keep thinking about it myself, but I like shooting centerfire too much.)
Correct: Rimfires do not draw from a holster (though if you want to carry it around in a holster as opposed to in a bag, you may), and extra magazines are not necessary as long as you have
two and preferably a friend along to load one while you shoot with the other one. That being said---shooting the Glock conversions and bringing along all four mags will make your shooting a lot easier, as people will only need to reload one mag while you shoot the rest.
Just one magazine will mean that we'll have to stop while you reload between each string, and that won't work very well. Two mags is workable, though.