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see........PADDYWAGONTOURS.COM /

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You can certainly hire a minibus with a driver/guide in Killarney. Quick google found me Buckley's Tours as one operator offering this. This side of the pond, a "van" is a commercial goods vehicle, you need to look for "minibus".

You wont' find an organised day tour from Killarney to Cork any more than you will find a tour to Las Vegas from the Grand Canyon, it's in the wrong direction. Most people pass through Cork on their way to/from Killarney, though I appreciate if you are flying in and out of Shannon you may avoid it.

I would suggest you consider hiring 2 cars. If you hire cars somewhere large, like an airport where flights from the USA land, you should be able to get automatics, they usually keep a few for people like you. With 3 per vehicle, hiring cars will be economic in comparison to transport and tours. Also it isn't easy seeing the sights in western Ireland without your own wheels.