I would check with the civil engineer in your area and see if there are any building code that pertain to this, as I am from Montana and the rules vary from state to state. If there is no code I would pour a footing 2' wide and 1' thick for the length of the whole structure and dig 4' deep post holes under each column to make sure it won't tip over. And yes I would put rebar in it.

"Before you criticize someone, walk a mile in their shoes. That way, you'll be a mile from them, and you'll have their shoes."