The breeder of our BCs gave them a small rawhide bone to chew on the journey home when we collected them at 7 weeks and they have gnawed on the occasional rawhide bone (now the much larger version) ever since (Always very well supervised).
I put combinations of Arden Grange Puppy, Nature Diet or Natures Menu (Puppy version), Cheese (chunks and cream cheese) and Natures Menu chicken treats into their Puppy Kongs...Sometimes they had Banana/Apple and ProBiotic Plain Yoghurt instead (Sounds like dinner followed by dessert doesn't it?). They also tried raw chicken wings at 10 weeks of age...and loved them.
As for training treats? I used cheese, baked liver, small pieces of chicken and Natures Menu chicken treats...They worked hard for all of these