A man's relationship to his mother is a complicated, fragile thing, like a crystal chandelier that you used to live inside of. Assuming there's no Springer-style reason for them to hate each other, most dudes love their mothers, but by and large don't "like them."
Personally, my Mom is one of my best friends, but I've found that I'm in the minority in that regard. For most guys, the teenage habit of hiding what you're doing from your mom never really wears off. It just becomes easier to accomplish and involves more unsavory things.
So while a guy will certainly listen to his mom when she talks about his dates, I doubt most modern men over 25 will actually take their mother's opinion as a heavily deciding factor...within reason. I mean, he (and you) are going to have to see this person no less than twice a year, and no one wants to deal with feuding in-laws.
Meshing with someone's family can be make-or-break, no question. But don't think you're going to get dumped just because mother doesn't think you're up to her little angel's standards. If he likes you, he likes you.
And in fact, quite a few of us will find some minor level of parental disapproval to be a powerful aphrodisiac. It reminds us of the thrill of sneaking out of the house to go to a punk show and making out in the parking lot. Something I never ever did, but have seen a lot in movies, so it must be true.