Supplemental Letter of Recommendation: should I submit it?

Hello!
I am a Brazilian high school senior, STEM oriented student. I have lived in Brazil all my life, and study in a traditional Brazilian school.
I will be applying to undergrad school this year, and was wondering about extra recommendations, because, just today, I received an offer from a Columbia professor to write one. My concern is that this professor, while having worked for years in the admissions office, does not know me at all. He is the father of my dads work colleague, and, while having had access to some of my work and research, he does not know anything about me as a person. I already have three recommenders from school, and they all know me pretty well, but this one is a Columbia professor and has worked in the admissions office! If he is offering a recommendation, it would most likely help my application, right? Although I have been reading the web pages of Yale, MIT and Columbia, my top 3 choices, and they all say that extra recommendations are only advisable if they add anything that hasn’t been covered before and if the recommender knows you well. I am so confused!

Don’t. A letter from someone who does not know you will not help. Adding extra recs beyond what is allowed will not help. It will just irritate the admissions board.

Thank you! I kind of expected that, but was hoping that the answer would be different… it is not everyday that you receive an offer of recommendation, and from a Columbia professor, no less, so I am a bit disappointed that this will not help me at all. I am a little worried about my other letters as well. My teachers in Brazil have never written recs before, and the Brazilian university admissions system is solely based off a standardized test score (no recommendations, no school transcript, no essays and extra curriculars are not listed in the application, and are even discouraged in my school), so I fear the letters will be generic and/or based only on academics. This offer was my last hope of getting really good recommendations, but I guess I’ll try to talk to my teachers and help them in the writing process. Do you have any advice for this problem?