We have a three year old male lab and a two year old golden/lab cross. And of course 5lb Ranger. He thinks he is a lab, but much smarter of course
Our big dogs let him do whatever he wants. I may worry about a lab puppy though- they are so clumsy and big! Have you considered adopting one that's past the real puppy stage? Both ours are rescues and are wonderful!
Good luck!!