So, the ideal way would be to rent the van from the 2nd to the 7th. We would ether meet up or pick up people and head out on the 2nd and stop somewhere along the way for the night. A good pick might be Cleveland because the site is only about an hour and a half away. That means we could all sleep in and relax and even check out the city a little before heading over.
Now the trip from the Cities to Cleveland is about 14 hours nonstop, so that might be a bit much even though it would be kinda nice the fallowing day so another option would be to stop in Chicago. Now this could work out well because we could pick up any stragglers from there and finish up with about an 8 hour drive the fallowing day.
Ether way, we could be heading through Chicago so we could try and fill up the last few seats. Also, we would probably stop ever few hours just to stand up and move around, as well as getting gas.
Then on the way back, we could once again go half way and stop for the night, or just have a couple drivers take turns and push all the way though the day. We would get back sometime around 4am that way though, so not sure how people feel about that.
If you take the fuel ($300), the rental ($100 - $200), the trailer ($50), and getting a couple cheep rooms ($100 - $120) the trip is going to be spendy, it will be cheaper then flying out or driving by your self though.