There is no need to limit the books with 4E, rather limit the players to legal characters created with the builder, then you will be fine. The only thing you should ban is an essentials character, we are holding off on the new online character builder in our campaign, wic has all the essentials stuff in it, because we suspect there is a big jump there. If you use the installed version of CB you will be fine.

None of the 4E material up to essentials should be banned, as there is nothing broken (especially after errata).

If I were you I would look up some tips on using the skill challenge concept. It is a good addition to the game. We also make rituals cheaper as encouraging there use makes things more interesting in the game.

GM