You're copping out of opportunities if you're using your age as an excuse for not getting work. I would actually argue that adults prefer seeing younger acts. It's more entertaining to watch a kid excel in a grown-up talent. You should capitalize on your youth and advertise it seriously. I'm sure you'd get more bookings for birthday parties and private engagements. I know kids who actually got full-time restaurant gigs, because they pursued the management and used their age to their advantage. I've also seen some very, very successful buskers no older than 13. They would get so much bank when they passed the hat, simply because the audiences thought they were cute, entertaining acts.
Follow your mom's advice. Get out of your room and start working. Think creatively. Get a gig and have some fun.
RS.