I would like to see them go on a "photo safari." In these days of budget cuts, this would not mean going someplace exotic and photographing, like it typically does.
They could start by each picking out a car that would be good for a photographer. As a photographer, I would look for something that's powerful enough to get me to good light before the sun sets, rugged enough that I can put my dirty boots and gear inside, but also sleek and stylish enough that I can drive it up to my next gallery opening, get out, and not be embarrassed. It would also have to have enough boot space (that locks) so I can stash away my camera gear without worry (no convertibles or open-sided jeeps, thank you very much.)
Then, for a challenge, they would each have to take still photos (using camera gear of their selection) while riding as a passenger in the car. Since "drive by" shootings have become quite popular, they would each have to make a small set of "drive by" images and present them as part of the challenge. They could even do a mini "gallery exhibit" where they auction off prints to raise money for charity (or some such thing) with the winner being the one who sold the most prints or received the best review from an art critic.
I think it would be fun and easy for them to do and I'd be curious to see what kind of "drive by" shots they would each get.