I hate to be an old fuddy duddy about this, but the Appendix I referenced above starts by saying:
NetApp recommends that you hot-add one disk shelf at a time.
If you want to add all three at once, you'll be violating the recommended approach. You can proceed, and it will probably work just fine if you do it correctly. But since adding multiple shelves simultaneously isn't recommended, there is no documented "correct" method.
The main thing is to ensure that the three shelves have unique shelf IDs. Shelf ID uniqueness must be maintained among all shelves that will be connected to the loop in the final configuration. Be sure to set the shelf ID with the selector switches BEFORE you power up the shelves. Interconnect your 3 shelves as you normally would, then connect the first shelf to your loop in accordance with the instructions for connecting a single shelf. Just use common sense, and I'm confident you'll be fine.