My 5 year old kid is addicted to minecraft and there is no way to prevent violence (you can always keep killing animals even in Creative + Peaceful mode). The problem is that 5 year old have little context on consequence and they really get intrigues in exercising new power they have. I'd like a pre-schooler mode which actively discourages any violence. May be if you try to kill something, an alien would descend and take away all your assets. So only thing you can ever do in Minecraft is just build something :). If someone can add this feature, it would be AWESOME!
If that sort of thing bothers you, I'm not sure it's possible to make a version that totally avoids it. Even breaking blocks is "enjoying destruction". I certainly enjoyed smashing all the bricks in Mario when I was little.
That said, I suspect most 5 year olds can figure out that virtual cube pigs aren't real, and that there's no consequence to punching them with virtual cube arms.
You might want to try the free game Minetest [1]. It is very similar to Minecraft but the basic version, minetest_game, has no animals. You can add mods that give you animals if you want them but they are not necessary. There are hundreds of open source mods to choose from or you can write your own mods in Lua. I learned Lua by examining the mods that come with the game and changing them. You can play in a mode where you can't take any damage. Multiplayer games can enable or disable PvP.
