If your kid owns an E-dirt bike, check on them.
As an old man, I ride my bike painstakingly slow down Alki beach a lot, and on multiple occasions I've seen a young man, teenager age, on what looks like a small e-dirt bike, zipping in and out of foot traffic on the busy sidewalks of Alki. He wears a black full faced helmet, has dark hair, wears a black hoodie, and has a red lanyard on his handlebar.
He doesn't announce when he's passing, and his bike is fairly quiet. Parents have had to quickly pull their young kids out of the way to ensure their safety. To his credit, the edirt bike rider does look like he has control, he flipped another rider off today and didn't swerve an inch while looking back. But in all seriousness, he is riding his bike at an extremely dangerous speed. Well over 20 mph. Way faster than he should be on any sidewalk, and I'm worried he's going to hurt someone or himself.
I get it, speed is addictive, and I can't offer a solution where you could open a bike up like that and experience max speed. But it definitely can't be on the Alki sidewalks on a busy weekend. Check on your kid before someone gets hurt.