You must know how far you're are going to push your concerns and what outcome you are willing to accept.
Let my tell you my own story from the perspective of the child.
I met a woman who was the manager of a hotel I was staying at long term. This was a higher end hotel and they would host a manager's reception at least once a week where dinner and drinks would be provided. Now, as I was staying there for month, I used this opportunity to cut my grocery bill down and get a few free beers. In course the manager would be there and we would chat, this grew over the course of my time there as we would see each other at least twice a day in passing and eventually a friendship formed. As time went on I realized that there might be more to this a friendship and tried slyly to get her out on a date, which to no avail as hotel staff are not allowed to date guests. After about 6 months it was time for me to check out and return home. I had resigned myself that I would never see this woman again as I we would separated by a good distance and I would have no further business in the area. Upon leaving I gave her my number as a last effort. I was happily shocked a week later when she called me and asked if she could still take me up on all those dates I had asked her on before. And so our courtship began.
To try and keep this story a bit shorter I will fast forward two years of wonderful experiences. She had met my family early on and we all had a great relationship. My parents, siblings, and extended family all seemed to love her and accept her as part of the family. I was quite enamored myself and decided that she was the one and it was to pop the question. And of course she said yes.
Fast forward a few months later, after my parents hosted an extravagant engagement party, save-the-dates had been, and wedding planning was well under way. This is when I am practically blind sided by the fact that my parents and siblings were concerned with the choice I was making, (like yourself has reservations about her character, that I was confusing lust for love, etc.). They had an "intervention" one weekend, where I come to find out that they went as far as hiring a private investigator to dig into my fiance's background! I was mortified, and once I told my fiance she was even more devastated, we broke off our engagement.
After a few months, I reconciled with my fiance as we be both realized we loved each other and the concerns of the outsiders were unwarranted. So, we kept the wedding and still invited my family to try to maintain our relationship with them. It did not go well.
My family made the wedding day absolutely awkward as they still felt I was making the wrong decision. It was so awful that after the wedding I ceased all contact with them!
A bit of context, my wife is 10 years my senior and when we married I was 24 and she was 34. She was previously married, and was a foreigner (but living here in the US as permanent resident.). However, I still have no idea as to why my family thought I was making a bad decision; sure they gave reasons and thought she was a gold digger and misleading me.
Still after six years of blissful marriage and two beautiful children my wife's and my own relationship with my parents is not the same as it once was. We only reconciled after the birth of my first child (and their first grandchild), and it look a lot to even get on speaking terms. There is always a tinge of awkwardness that lingers at all family functions.
TL;DR My family had similar misgivings about my potential wife, they pushed too far and nearly never heard from me again.
You must be willing to accept a similar outcome even if your relationship with your son has been stellar up to this point. You may not go as far as my parents did, but you are still calling into question a huge decision of your son. Look at it from his perspective, you are questioning what is right now one of the "great truth's" in his life, "He loves this woman, he knows it, and you are not going to tell him any different".