I agree with SafetyMom - why not use Magical Express? It's the least expensive (aka free) mode of transportation between MCO and any Disney-owned resort. Sure, the Lynx bus is "only" $1.25 per person BUT - you take the bus from the airport to downtown Orlando (northwest when you want to go southwest) then transfer to a bus that drops you off in the Magic Kingdom parking lot. From there, you need to take the monorail or ferry to the Magic Kingdom, then board the bus for CBR.
There's always the Mears shuttle - about $17 per person one way, you need to wait for the vehicle to fill, then who knows which stop you'll be? My 'luck' has always been that I'm the last one dropped off.
Then there are taxis and town cars, prices about equal - $40 to $50 one way, plus tip. Town cars need to be reserved in advance; a taxi you can just get in line outside arrivals. Or, for somewhat more money, you can reserve a limousine.
Or you could rent a car.
But you DID ask for the cheapest way, and DME is it!