Game Help.

Lego Star Wars 1 and 2 and Lego Indiana Jones meet all of those except for playing on other computers. It has a co-op mode for playing at the same computer with up to two players. They are retellings of the stories from the movies where you play as lego characters and have funny cut scenes. You don't even need a beefy computer for them.

Doom 3.
Dark Messiah of Might and Magic.

Nah, just kiddin'. Seriously, though, I'ma recommend Black and White. You play as a god and raise a village and a giant creature, like a lion, a monkey or a horse. If you do mostly good stuff, like use miracles to restock food supplies, or wood, or resque drowning people, your alignment starts to shift towards good. If you do mostly evil, albeit more fun, stuff, such as throwing boulders at buildings, using miracles to set people on fire, or throw people for miles, your turn evil.

You raise your creature by training it do do things like you would a normal pet. It has its own alignment which isn't swayed by yours. Kinda like a more advanced tamagotchi.

If you're good, your temple and hand start to glow, and look "good", and the same with evil, but don't worry, 'cause the evil isn't that scary or evil looking, your hand just goes red and gets claws. It's easy enough to stop him doing evil stuff, though, 'cept I found destroying things more fun.

Well I know one but Im waiting for it myself i think it comes out summer of next year.
Three words Kingdom Hearts 3

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.

Monkey...Island? :/

Yeah, why not? 'Sold, but doesn't make it any less of a game. I played it loads when I was a kid. I still do, sometimes.

Adding a vote for any of the Lego games, I know you can Co-op on the same PC have no idea if its possible for it to Co-op on a network though, have A: never tried and B: never actually looked at the multiplayer options.

Need for Speed.. I think it was number 2 or 3 had a good network options if your after a driving game and Red Alert/ Command and Conquer can certainly do network play if you want something more strategy orientated. A slightly older game would be Soldiers Heroes of World War II, its strategy with the option of direct control of the characters too, personal load outs salvage weapons and vehicles very destroyable terrain and essential a really solid game with the option of networkable Co-op.

Um, monkey island and Sam and Max are full of adult humor, and the old sam and max has some pretty strong language.

I played, and enjoyed, both of them when I was about 6...

Monkey Island is a game where the resident cannibals are vegetarians and pirate crews are made up of singing quartets with only three members.

No "strong language" from Sam and Max springs to mind, care to provide some examples?

It's not so much that the adult humour makes it unsuitable for kids, more allows adults to appreciate it more.

'Sides, you've really got to think outside the box, so to speak, to solve a lot of the puzzles, something most games now don't make you do enough. Such as bungee jumping from one of Mt Rushmore's noses and collecting a cup of tar from a pit below, to stick fake wooly mammoth hair and a wig to a boiler suit to make a bigfoot costume. Or cutting down a rubber tree to use in a caber tossing contest, to rig it so you win.

I could have sworn the little bunny was a foul mouthed sociopath. Maybe I'm remembering something else.

I really recommend Trackmania Nations Forever. Its a unrealistic car game where you ride around in crazy loops and jumps and where you can play against people from all over the world, or on network. You can also make your own tracks and play them with a computer or your friends. It works on pretty old computers, and still got options so it looks great if you got a new one. Theres a gentle learning curve in it, its really easy to learn but you can spend months on it and still find many things challenging. Its totally free, but if you like it i recommend you buy the full version, cause companies like that deserves support from gamers. I'm not allowed to post links before i get 50 posts on the forum, but you find it on trackmania dot com or filefront.