You are smart to worry. Bubba weighs 96 pounds and is strong as an ox.
He's pretty well mannered, but if he really decides to go somewhere, he could pull me down and I'm rather small. I use a prong collar which slows him down (a little).
Just be sure he's well-trained and you'd probably be okay.
There are some of those really big dogs out there... especially in field lines. Not sure why they want to breed such a big dog, the purpose of the Labrador was to be short coupled dog, compact enough that you could fit him in your duck boat, and help him back in after a retrieve! Ah well.. The breed standard is still the same, and finding one with parents within this range should not be difficult if size is an issue.
Size, Proportion and Substance Size--The height at the withers for a dog is 22½ to 24½ inches; for a bitch is 21½ to 23½ inches. Any variance greater than ½ inch above or below these heights is a disqualification. Approximate weight of dogs and bitches in working condition: dogs 65 to 80 pounds; bitches 55 to 70 pounds. (American Kennel Club - Labrador Retriever)