"Most events that we do in the
ballroom are educational, and collecting door money could fit into a
donations framework pretty easily."

unfortunately, unless a group that rents the ballroom is ok with making the event appear as though the omni is hosting/organizing the event, i'm afraid the group would have to be fiscally sponsored by the omni in order for the $ to be "from a charitable source"...even if the event is educational.
~r