Relationships Help!

Hiii friends, 
Questions and opinions: my girlfriend and i broke up a few months ago because I cheated. I feel super shitty about it but we talked about everything and decided to work things out (I know, you are thinking "you're girlfriend is a dumb ass for taking you back) but it was a mistake and I know I did wrong. If I could I would take it back. 
My question to you is: 
1. should I apologize to her parents? If yes, what would be the best way; Text? Email? I'm sorry flowers? Card? 
2. What should I say?