In some cultures it's common to give kids coffee. My parents didn't give me coffee when I was a kid but my wife's parents started giving it to her at an early age. My kids both drink coffee. My older one started on black coffee when he was 2. It's just a routine part of his day. Coffee at breakfast and then at cafecito in the afternoon.
Coffee has been shown to reduce the length and quality of REM sleep, which is very important for early brain development. Read the relevant section in ‘Why We Sleep’ and you may change your mind.
