Um. Green tea is good for adults. Caffeine in large amounts is bad for kids. ESPECIALLY TODDLERS. In most cases, a cup of tea has more caffeine than a cup of coffee. I've done the experimentation in labs to KNOW - it's just a different type of caffeine. Chocolate has caffeine too. Think about giving a toddler a hersey bar instead of the tea. It's the same difference.
Also, you better be ready to work out because it'll make them super hyper. Kids react differently to caffeine than we do. You never know if they'll burn out or how quickly it WILL damage their liver and kidneys.