He said he'd teach me how to drive...?

The other day, myself and my family friend, who is 30, met up and went out to eat.
I was talking about how I really need to get my license because I'm 17, will be 18 in a month, and still don't have a permit nor a license. I went and got the drivers manual a week or two ago but haven't even attempted to read it. He said, "I'll make you a deal, if you read the book... I will teach you how to drive." I literally thought he was joking. He replied, "I'm being dead serious. Read the book, and I'll teach you how to drive. We'll go find an empty parking lot or something and I will help you." We shook on it and stuff. I told my Mom and she was like, "Take him up on it! He's always followed through on stuff!" So, I guess he just might be teaching me how to drive. I'm really thankful that he's willing to take time out of his day and life to teach me, but I'm just nervous because it'll be in his car, I don't want to look like a dumb a*s, screw up and be this super sketchy driver. I've driven some before, but I do differently in different cars and depending on who is in the car. Should I just take him up on it? Or say, "Thanks, but no thanks." And have my Mom or Dad teach me?