Should I have exposed him privately?

TIFU by inviting my fiance ex best friend to our engagement party and accidentally exposing the biggest secret of my life. My name is Rachel and I am twenty eight years old. I was supposed to get married in three months to a man named Derek. We had been together for four years. Everyone said we were the perfect couple. I believed it too. Two weeks ago we threw an engagement party at my parents backyard. I invited everyone including my old college roommate Jenna. She had not spoken to Derek in over a year after some falling out I never understood. I thought it was ancient history. I was wrong. The party was going great. Fairy lights everywhere. My mother crying happy tears. Then Jenna walked in wearing a bright red dress and everyone went quiet. Derek turned pale white. I remember thinking that was strange but I brushed it off. I walked over to hug her and she pulled me aside. She said Rachel we need to talk somewhere private. My stomach dropped instantly. I told her this was not the time. She grabbed my wrist and said trust me it is exactly the time. We stepped into the kitchen. She pulled out her phone and showed me messages between her and Derek from eight months ago. They were not just messages. They were photos. Photos I cannot unsee even now. My hands started shaking. I asked her why she was showing me this now at my own party. She said because Derek begged her to stay quiet and she agreed only if he ended things with you before the wedding. He never did. I felt the room spinning. I walked back outside where Derek was laughing with my father like nothing was wrong. I grabbed the microphone from the small speaker system meant for toasts. Everyone looked at me confused. I said I have an announcement. Derek smiled nervously thinking I was about to say something sweet. Instead I looked directly at him and said we need to talk about Jenna. His face went from confused to terrified in half a second. I said in front of everyone that he had been cheating for eight months and lying to my face every single day. Gasps filled the yard. My mother dropped her wine glass. Derek tried to grab the microphone from me but I stepped back. He started saying it was a mistake and it meant nothing. I asked him why he proposed to me while still sleeping with someone else. He had no answer. Just silence and sweat on his forehead. Jenna stood by the door watching everything unfold, arms crossed, no longer scared to be seen. Some guests started leaving immediately. Others stayed frozen, unsure what to do. My father walked over and quietly took the microphone from my hand. He did not say a word to Derek. He just looked at him with pure disappointment which somehow felt worse than screaming. I took off my engagement ring right there in front of forty people and placed it in Derek palm. I told him the wedding was officially cancelled and so was every promise he ever made me. He tried to follow me inside the house but my brother blocked the doorway and told him to leave before things got worse. That night I found out from Jenna that Derek had actually spent our engagement fund partially on secret dates with her while telling me we were saving for the wedding venue. That detail hurt more than the affair itself somehow. Now people online are divided. Some say I should have confronted him privately instead of destroying his reputation publicly. Others say he deserved every second of public humiliation for lying that long. My mother says I should have waited until after the party to avoid embarrassing our family in front of relatives. Honestly I do not regret a single moment of it. Was I wrong for exposing my fiance secret affair at our own engagement party in front of everyone we know.