Id use this to teach your grandson that a dog is alot more responsibility than he thinks. How old is he now??
I have 3 y/o daughter and she *thinks* she wants a lab of her own. Im glad she taking after her momma (me

) but there is alot of work involved in owning a Lab and I know she is not ready to accept the responsibility of having her own.
I think maybe when she is 8/9 years old I will start asking her to feed my Lab everyday. If she can feed/water/train the lab on her own without being asked then that speaks volumes that she is ready for one of her own, but she'll have to use her own initiative.
Now back to pugs. I think maybe what you can do is have the pug live with you BUT he can come see the pug and play with him when he's there visiting. This way you have the best of both worlds. The grandson is happy because now he has a pug at Grandma's house, and when he's there he can take care of the pug for the day he is there including feeding, watering, walking, bathing ,etc. This ensures he gets the hands on learning without the burden of full responsibility for the animal - which may be a relief for his parents.
Good luck on your decision - and I agree as a Lab owner that pedigrees are important - they up your chances of having a sound dog.