I'll usually compare one way flights from DTW to MCO with Spirit, Airtran and NWA. More often than not we end up flying one airline out and another home. All three of those airlines offer non-stop service from DTW to MCO.
With Airtran you can also check Flint to MCO. And, Allegiant Air also goes direct to MCO from the Lansing airport.
If you'll have a car you might look at flying into other airports in Florida. We've gotten great deals flying into Tampa or Jacksonville before. A year ago we flew USA3000 home from Fort Myers for $75 - we didn't have a car with us but we rented a car from Avis in downtown disney for $35 and droped it off at the Fort Myers airport. In November we flew Spirt to Tampa ($69), again, rented a car at the Tampa airport and dropped off same day at the WDW Dolphin ($45) and then flew on Airtran from MCO to DTW ($99)....so RT that was under $200 per person even with the car, and having the car gave us the ability to stop at the grocery store before getting to our hotel.