Good job! See my corrections below. 

Write an Email

Hello Alex!
I'm really suprised about by your e-mail , because just a few days ago this idea crossed my mind. I'll be definitely there!
Don't worry about that, I'll send you some videos from YouTube for you to get to know them better. I've always loved rock music, but they made me realize how much I need it in my life. They're awesome musicians and really funny guys! You will set your heart on love them! 
I would rather be stood up in the front row than sat on the grandstand (Not sure what this part means. Maybe I just don't know this expression?). It's really exciting to share the experience with the rest of the crowd!
I'll be pleased to spend the next day with your parents we could have lunch together and then go for a walk. I know how they love long walks.
All the best,

Helena