Hi dntd, welcome to the forum. I just saw your other post and picture of your new little baby - oh so adorable!! Do remember that he's only been in your house for a day, so even he probably doesn't know what he likes yet. Give him some time to adjust to his new surroundings and his new life, without worrying about what would be the best toy or food reward. Let him get to know you, your husband, and your other dog, find his way around the house, and feel like he's really home now. You indicated that he'll be helping your husband, but don't start worrying about that yet. Heck, 2 mos ago, this little baby wasn't even born! Give him a little time to get to know you, you take a little time to get to know him, and you'll figure it all out. He's still very nervous in his new surroundings - let him relax and figure it all out. New dogs, no matter what age, need a week or so in their new homes to really get used to their surroundings. Give your little puppy time before you start in on him - you have loads of time.
As far as the best toy to use as a reward? The best toy is the toy that your dog cherishes more than any other toy - and that's different for every dog. You'll figure that out in time, too. Right now, go play with your puppy!! :-)