2nd emma82, socialise them together, you supervise. If the puppy gets at all dominant with your child flip him on to his back and make you hand into a claw and press (firm but not hard) your fingertips into his neck area. This simulates a bite telling him he has overstepped the mark. It's a bit 'ceasar milan' but it works. Better for the dog if your child can do it, but 14 weeks is a bit young!
You have to be the boss, then your partner, then your kid, then the dog. He'll be happiest that way.
And never, ever, leave them alone. 99.9% of the time you'll be ok. A friend of mine had half her face bitten off by her family's golden retriever. She would have been really pretty but her face is now a jagged mess of scars….