It's going to be the same for 4 people!! No difference in price.
But..if you're trying to cut costs, try the Mears shuttle from MCO. It will cost you about $18 one way. You can't book it in advance if going to a WDW resort, but you can just head down to the counter at MCO and pay for it when you arrive. You could take it to the Contemporary and then walk over to the MK.