I don't think age has a lot to do with it. Don't get me wrong, a fresh P plater is obviously more likely to crash, but I don't think you can say a 20 year old is a worse driver compared to a 30 year old, just because the 30 year old has had more driving time under his belt. I think you can drive or you can't. And as far as i've seen, on all the cruises, most people here seem to handle there car pretty nicely.
My 2c.