I really like the idea of breaking up the game into three different modes of play. I can imagine the classes excelling in different modes. That sounds pretty cool to me.
Like Nevvur said, in your situation there's no reason to do AL unless your players want character portability. Otherwise, it's just going to straight-jacket you as a DM. You also don't need to be running AL to have other players DM. Just cross your fingers and ask!
I don't want to knock AL...
They're shipping it from the United Kingdom so it's expensive. I noticed that Cool Stuff Inc. has it $41. And I bet the shipping is cheaper too. I may switch my order over.
http://www.coolstuffinc.com/p/243636