Currently there is no smooth way to do collaboration/delegation with Omnifocus. OG plans on making us use OmniPlan to do any sort of Group Collaboration with OF in the future, which is a little strange.
Have you tried Wunderlist on iOS, OSX, PC. It's free and allows you to collaborate to your hearts content. It is nowhere as robust as OmniFocus, but I find it useful for sharing lists with my wife. It's great for maintaining Grocery Lists, House Tasks, Shopping Lists, etc.
http://www.6wunderkinder.com/wunderlist/
OmniFocus was really designed for the individual user. The present reality of work is all about collaboration and delegation, so I hope they implement this much needed feature sometime soon...but until then, you will have to cobble together your optimal workflow.