Pugs and Labs are two totally different breeds, fyi. lol. Be prepared for a TON of work with a Lab puppy-- they are typically a super rambunctious breed and take a long time to mature at all, sometimes 2-4 years. But basically stay a puppy for their whole life. My grandma's 9 year old Lab is still hyper as ever. They are very bouncy, jumpy, pups and definitely need to be trained starting young (as do all dogs, but Labs in particular just seem to be super hyper as puppies).
Pugs, on the other hand... while they CAN be active dogs, in general the breed is not super active and would be glad to lay around all day or for a few days if necessary. A Lab pup will not LET you skip a walk, whereas a Pug would probably love to skip one.
lol. Also, Pugs shed like CRAZY! I have never met a dog that sheds more than a Pug (with that thin hair) except maybe a Lab, haha. So both are huge shedders. Also, Pugs in general have quite a few health problems even with responsible breeders so be prepared for that. They also can't always tolerate the hot weather, since they are a brachellyic breed (smooshed face) and are prone to getting overweight and having breathing problems.
Just research both breeds extensively and don't go into it lightly before just letting kids pick. I've found it's always a bad idea to let kids pick a breed they want. My dad did it with me and I picked a German Shepherd and we ended up not being able to handle what she required or train her properly, and she ended up getting put to sleep at the age of 4 when she attacked someone.