Some working types are harder work because they are instinctively on the go all the time (Springers, for example). IME working stock Labs are less so than others. My friend, a rescue owner, has several Labs of his own and those waiting for homes and they are all much of a kind, lovely though.
I have a Lab X and the family have had Labs, brilliant, loyal, loving dogs. But I've got to say this, from personal experience... if you have a favourite breed and adopt a different one you may ALWAYS hanker for your first choice. For me the perfect breed are GSDs and when I lost my first to incurable illness I swore one day I'd have another. Then six months later I lost my my SBTx to a stroke and I was left with just my Lab X, whom I love to bits. It wasn't the way I wanted it to happen of course but then, with my Lab x grieving I searched for a new friend and there was only one choice.
Had I adopted a different breed I know that I would have always been sad that I hadn't opted for a GSD, no matter how lovely the new dog.
I'd ask you this - are you going for the Lab because you really, really want him, or because you can't find a Newfie pup and are aching for a dog and impatient? Not meaning to be rude and I'm not insinuating you'll regret choosing a Lab or give him up in 6 months time, but will he be enough for you or will you always be wondering "What if I'd waited..."?
Of course, it may be possible that you can opt for a Lab now and have a Newfie as well, when one comes up, but if you feel that you can only have one dog perhaps waiting might be the right thing for you to do.
These are just my thoughts of course, you may see it entirely differently. I just know how it feels to adore a special breed.
Whatever you choose, good luck and I hope he and your family will be happy together.