Tip is included in your fare with Lansky's. However, if they go out of their way to do something extra and nice for you, I am sure a tip would be appropriate. At least that is the answer I received when I asked the same question.
The tip is supposed to be included. We use them for every trip, and only tip when we get particularly good service. Yes, that does mean there have been a couple of times we didn't tip at all. Thankfully, most trips we're pretty happy with the service, and I usually give them $5-$10. (Note, there are two of us, so not much luggage to help with.)
I typed, but that's because our flight was large, we were slow getting to baggage claim, and it was me and 5 excited kids. Probably not the most fun trip for the driver. I tipped 15 because he pour up with a lot and wad stool cheerful and pleasant!