mobile truck delivery idea

im tossing around the idea of employing a three wheel bike for "mile radius delivery" from the trucks current location.....
 
after i set up at location, i would tweet and FB the location, and offer free delivery within say a mile radius for the time i am at that location.... the kid doing deliveries would take the phone orders, process payment, hand order off to me, then pedal like a mad man........
since this is a military town, could call it something like the "drop zone"...... would be mainly a downtown thing
 
has anyone tried this, have any thoughts on it ? am i grossly underestimating the logistics of something like this ?