bikes are a pain to carry by bike. there's a chance free ride has a trailer that you can use, or use as a model. some folks made one that's basically a car roof rack attached to wheels. i guess it only carries like 3 bikes at a time tho. i've used a kids trailer for years, and it did well as a cargo trailer until we used it on the keg ride a few years ago. it didn't do too well then.
the best luck i've had, unfortunately for you, is with a bikes at work trailer. i think i was able to haul around 9 bikes at once on that thing.