In stead of a bachelor party......
First of all, you have a great idea. I went to a bachelor party once. Once was enough. A shooting event is a lot more wholesome. I'm not real big on timed events unless all participants are experienced enough that safety wouldn't be compromised for speed's sake. One of my favorite targets is a milk jug filled with water. When hit with a high velocity soft point they are fairly explosive yet easy to clean up. If you have some participants that are inexperienced, try to have some events where sheer luck will readily trump the most skillful. Or you can handicap the better shooters. Prizes for skill and even more prizes for luck. The point is for everyone to have a great time. Like Scotch Doubles where the all-stars can't dominate the game. Remember that too much competition becomes anti-social. Have an excellent time and let us know how it all pans out.