
If you have a very forward puppy, you might swerve the Minor Puppy class, but that won't allow for your puppy misbehaving perhaps!! If you want experience, for both of you, then by all means put him in all the classes he's qualified to be in, remembering that once he's beaten in a class, he can't progress any further (ie for BOB or BP). Personally I'd only enter more than one class at one of the lower shows - eg Open. If you go straight into Champ shows, just enter one class, and to begin with, I think that should be Minor Puppy. His breeder should be the one to assess your puppy, and advise you - as his breeder, she'll be bound to want him in the best class, for him, so he does well for you.
You always have to bear in mind too that showing can be stressful for a puppy - so introducing him gradually (just the one class) may be better for him.