Pete - be sure to try to teach them a soft mouth now. Once they get their adult teeth in it is a lot harder to 'reset' their bite. Whenever you play with them and they are too hard on the skin, yelp and recoil like an injured puppy. High pitched. For most puppies, this will make them second guess their actions. If they don't get the clue, end the game and walk away after they bite too hard.
Another trick is to feed them by hand. One kibble at a time. Put the kibble between your two fingers and present. When they bite too hard, yelp and pull the treat away. Present again. Repeat this until they mouth it gingerly, carefully. THEN they can have their treat. This teaches them impulse control and the only way they get their treats is if they are gentle with their mouth. It usually takes a week or two of consistent 'bite training' before you start seeing good, solid progress.
Now is the time to do it, while they are young, so hop to it ;)