Are you providing safe transporation from place to place? (i.e. buses). If so, you should probably make sure that any barfing on the bus will result in a $150.00 fine, payable IMMEDIATELY in cash.
This is a pretty good resource to see how it's done properly and safely:
http://www.bustloose.com/
Their pub crawl names include: SUMMER SLAM CLUB CRAWL and BACK TO SCHOOL BENDER CLUB CRAWL and they have Halloween ones, Stampede ones and Canada Day ones.