A lot of theme parks have staff that walk around selling things. Could have a guy with a big clump of balloons or a girl with a camera that will take pictures like many parks have inside the main gate that rush you and give you a ticket to go to a nearby stand and buy the park themed photo. Maybe have the same camera staff take pictures of guests with the entertainers like at an entertainer spot. Also there are the ever so prevalent carts with drinks or some food items. And, if there is some sort of restocking management that is implemented, the vendors could return (with carts if have) to restock/take their break all at once. This could add a whole new dynamic in the management as well as catering to guests. You already have the wandering entertainers that interact/are interacted with by guests so just add a financial transaction to that process. 
