The free shutte from/to (LBV) area hotels appears to run once a day in each direction. I don't see anything about an airport run, or that it goes anywhere near the airport http://www.lbvfs.com/Orlando-Outlet-Free-Shuttle.cfm. I do see that personal luggage isn't allowed.
AFAIK the shuttle from LBV outlets to MCO is free. It costs $12 per person to check your bags.
edited to add--Looks like for $15 they'll pick you up at your hotel, take you to the check in store and check your bags. You can then shop until it's time for your bus to MCO.