Also, it's a bit of a strech, but check out Monkey Island 1, 2, 3 and 4. Sam and Max Hit the Road, Or Day of the Tentacle. I mentioned them in another thread.
Monkey Island, you play as "Guybrush Threepwood... Mighty Pirate!", in the first one, you're on an adventure to become a pirate and resque your love, Elane Marley from the hands of Ghost Pirate LeChuck.
In MI2, Guybrush looks for the treasure of Big Whoop. This time, though, LeChuck's back, although you destroyed his ghost in MI1, he's back as a zombie pirate. You've got to get the 4 peices of the map to find Big Whoop and escape from LeChuck.
MI3, after escaping from LeChuck, you end up on a dodgem car, in the middle of the sea, and get captured by LeChuck. This time, he's after Elane, again, but he's bombarding her island with cannon fire. You cause LeChuck's ship to capsize and LeChuck to set his beard on fire. Whilst escaping the capsized ship, you find a ring and use it to propose to Elane. She puts the ring on, but it's cursed and turns her into a gold statue. You've got to counter the curse with an uncursed ring, with equal or greater value.
Can't really remember much 'bout MI4, it was a bit pants.
The MI series might be a bit of a strech, there are some pretty evil things in it... like LeChuck, but considering the whole series is set in the mind of a kid visiting a Pirate theme park, it's not too bad. (LeChuck is actually his brother, Chucky, who's looking for him, to take him back to their parents.) Very funny, too. You'll enjoy them as much as y'kid. They're point and click adventure games, y'know... stuff like picking up items and using them to solve puzzles to further the plot. If you want an example of the kinda stuff in MI, search "A Pirate I was Meant To Be", on Youtube.
Day of the Tentacle's about trying to stop an evil purple tentacle from taking over the world, with three characters, all trapped in different periods of time. It's a long and fairly complicated storyline, but your kid should still be able to comprehend it. Another point and click adventure game, 'cept older than the MI series, and the sequel to Manic Mansion, if y'ever heared of that? It's definately ok for kids.
Sam and Max (If you don't already know of them) is about Sam, a doggy-thing and Max, a rabbitty-thing, freelance police, as they try to find the Bruno missing bigfoot and Trixie, the giraffe necked girl gone missing from a circus freak show. Can't really say much more 'bout that, 'sok f'kids, though, still has some fairly dark humour, for older people, that'll jus' go straight over kid's heads.