Not sure it would be
fun the whole time. My 7-year-old nephew is on the chubby side and tires too easily from walking, and he's a freaking mama's boy (my sister has yet to cut the umbilical cord), and is a huge car slut so will only take interest in driveable things. In short, he's high maintenance.
My niece (11), on the other hand, is rather cool. She loves watching House and CSI on t.v., likes looking at gross stuff like body parts, is into true crime stories and ghost stories, and doesn't tire as easily.