I’m also coming to the conference this year.
I actually live in Prague (hi @chriskottom), so if I can help someone with information or something, let me know.
Regarding the shooting range, I do not know this one. I used to go to a different one in the center a few years ago: http://www.avim.cz/index.php?pg=home&lg=en. It was OK, nothing great. It was cheap and in the center, though.
I can completely recommend this indoor skydiving arena, though. It is an awesome experience while completely safe, and the people running it are fluent in English and very nice.
Another fun activity that I think is cheaper in Prague could be flying in a real commercial flight simulator. You get a basic introduction to flying commercial jets (Airbus 320), and then get to actually fly one in a real commercial simulator.