I would not recommend Linder Regional in Lakeland. I would recommend Direct Air even less.
It is more than an hour drive to WDW. The only major car rental is Hertz, but they do have a local company I've never heard of. They have three "airlines" listed, Direct Air, an in-Florida only service airline, and another small charter service.
Researching Direct Air, they are not an airline. They are a company that sets up charter flights, using multiple charter carriers. If you reserve through them you will not know who is the actual company providing the service. And charter companies have a propensity to cancel flights if they don't have enough passengers or freight.