How can I apologize to my friends mom?

It was a Friday and my mom got free tickets to an amusement park. I wanted to take my friends Tony, Aj, and Stephanie. Stephanie does not like my other friend Tristan and he was at Tony's before Tony's parents took us to Bush Gardens. I accidentaly invited Tristan and realized i made a mistake when I looked at Steph's face. Now I was the douche bag and told my friend not to come basically. I felt awful and now his parents know and his mom thinks I am a douche. I heard her say it when I was on the phone with him. He is a realllllly good friend of mine and I want to apologize to his mom for my mistake. How can I do this??? I need an answer fast cause there is a talent show we want to be in which means we need to be together to practice and I don't want it to be awkward around his parents. I know it was a dick move but you gotta hear me out and give me the best you can come up with! HHHHEEEELLLLPPPPP!!!!