I've worked on my fair share of games in my career. Most of the time we've been able to rely on combat in some form or another as the primary game mechanic. In the RPGs it was sword and sorcery type combat. In the WW2 games, it was shooting enemies with authentic World War 2 weapons.
Blood? Who cares? Dismemberment? Cool! These are things that game designer rely on every day to create conflict, drama, and ultimately, entertainment. I'll admit that it's fun to blast soldiers, or raiders, or fire ants into thin red paste, if you'll forgive the Wasteland reference.
I'm not going to get into the appropriateness of violence in video games,...that's a whole different topic of discussion. We can argue with Jack Thompson all day long over what sorts of content are appropriate for public consumption. I think we'll all agree though that exploding human beings like a blood sausage isn't the sort of content you want to be directing at 6-12 year olds.
So what's the deal? The biggest problem I've faced going from adult themed games to kid themed games is the inability to rely on game mechanics that we as designers take for granted.
Most games rely on some form of conflict to drive the gameplay. In shooters, that conflict is at the barrel of your gun. In RPGs, the tip of the sword or the end of the wand. it's the same with most strategy games.
So here's the challenge: try to design a core game mechanic that includes drama and conflict, but no one dies. ToonTown and Raving Rabbits plunger shooter don't count. Those games use non-violent versions of the same old mechanic we've used time and time again.
In the beginning of my time at Spin Master Studios, we weren't sure what sort of game we were going to make. Before I got lucky with a skateboarding MMO, I struggled day in and day out with potential solutions for game mechanics that are appropriate for children, but aren't necessarily just sanitized versions of the same old mechanics that we use time and again.
Of course, there are plenty of games out there rated E, and plenty of game mechanics available that they use. Sports games are one example, though you could argue that they're just sanitized versions of war in the first place.
Mario and Sonic are two other good examples of game mechanics that aren't exactly violent (though they are in their own way, killing Koopa's and such) but they are mostly appropriate for a young audience.
So here's my challenge to you...can you design a game based on an RPG or FPS mechanic that would be appropriate for children?