Ok, now I now that he races karts. My son and I spend the trip going home thinking about silly cart things:

Pie Cart
Ala Carte
Chicken Cart Pie
Wal-Kart
Cart-ridge
Pop Cart
Modern Cart
Three Cart Stud
Cart Blanche
Amelia Earkart
Cartheart overalls (ok, that's real)
4Kart symphony
Kart-y, kart-y hearty!

And then we spent an amusing time googling shopping cart races. My imaginary boyfriend enjoyed this immensely.