Wow, I'm afraid that's pretty overwhelming to deal with and like eeeefarm said, no way on earth to do it in a week. However, you do need to begin working on it soon and plan on a very long time to turn this around. Because this dog has shown he will grown and try to bite, your risk of him actually biting, and your legal liability are huge.
If you can buy or borrow a secure crate (they aren't cheap) that he can't get out of or hurt himself in, do so. If you can't, do what eeefarm suggested, and make darn sure that leash and collar are totally secure.
Once your nephew has left, please get a trainer to start working with your family and this dog on both children and crating. They are very important and it can be overcome.