I've just recently seen a couple of shows on introducing a new puppy. They recommend making sure that you greet and feed the first dog and so on first and then the new puppy. The dogs need to learn their order in the "pack". If you keep your status then the others can figure theirs out. Once your older dog realizes that he is not being replaced or crowded, they should be fine. I would still continue to keep them apart until the snapping stops. Make sure to be there when they are together. Make sure your older dog can have a place to be quiet if he chooses, this will help alleviate any anxiety that he may be experiencing. Good luck and keep us posted.
