We stopped at Bowling Green (KBWG) for an overnight and tour of the cave on our way back from SC last summer. The FBO was pleasant, I don't believe we had any extra fees, and they got us a crew rate at a decent hotel in town with free dinner & breakfast in the lobby.
The rental car took forever to arrive and was a smoker's vehicle, but that's partly on me for not planning ahead.
Our other option was KGLW but I wasn't able to verify we would have any ground transport options there to get out to the park.