Multimorphic P3, running any of Barnyard, ROCs or Cannon Lagoon depending on the age range demographic. Plus you have the option for the full Lexy Lightspeed for more serious players. The upcoming Cosmic Cart Racing is going to be effectively a "Mario Kart" with pinballs, so that might suit you too. Upfront cost may seem high, but the game selection and ease of switching between them makes up for that in a hurry.
Here's a YouTube link for a video of a friend playing ROCs:
Also check out the Multimorphic web site for a lot more info and video links.