So I have a group of players I'm playing D&D 4e with. Two of them are hardcore gaming nerds, my brother and his friend. His friend actually has a job but it's not intensive, my brother on the other hand has no job and is CONSTANTLY thinking about D&D. All he lives for is escaping reality. The other players are me, my wife, my 10 year old niece and her father. All of us are new, I have played lots of RPGs so I can handle myself but they're still trying to grasp the concept. Anyway what is happening is that we keep switching between campaigns.
It started with my brothers, then we went to his friend's with Dark sun, and now I'm trying out mine...but now my brother wants to play a NEW one he made. When I told him that it's really confusing for the new players to have to create entirely new characters with different classes and backstories he got offended. I asked him if we could all sit down and try to create a campaign world open enough that anyone could DM without spoiling their fun when they play like they know what'll happen. He argues no one would be able to have world-threatening or changing events, and the continuity would be screwed up. But I'm determined that this is the only way this group can keep playing without it getting chaotic.
How have you set up campaigns/worlds where everyone in the group can DM at any time, without causing spoilers or continuity issues? Are there any good references for building something like this? It's really the only way I can keep everyone happy without taking offense and confusion by the constant shifting of campaigns. Not to mention allowing the total noobs like my niece a chance to try DMing?