If you are training for protection (real protection, not schutzhund), then a kenneled dog is useless. Not only in a physical sense, as the dog will not be able to get to you if you need him, but in the sense that a dog who is stuck out in a kennel is NOT forming the extremely close, and supremely important bond that these dogs must have with their handlers to be effective. It is the BOND that ultimately drives these dogs to be effective protectors; all other drives are secondary to this.
Tips? Socialize the snot out of him. A protection dog should be exposed to absolutely anything and everything. They must be able to handle ALL situations with confidence and stability, and learn how to handle day-to-day life situations. Spend this time exposing him to the world, as this will be far more useful than anything else you can train with him at this point.
As for toys, I recommend a Kong, a nice tug toy/rope, and some bully sticks to keep him occupied.
GSDs- Mulder, Ridley, Vega
GSD on the half shell- Rigel