Here's 2 ways to go about it.....
1. Brew something only you will want to drink and enjoy it all yourself.
2. Brew something like a barley wine and age it until you can share it on his/her 21st birthday.
I wasn't into home brewing when mine turned 3 so I bought her a bottle of Johnny Walker Gold that will be 36 years old when she 21. I'm not looking forward to my little girl growing up, but I am looking forward to that 36 year old bottle of Johnny lol.
EAC - 5/2/14
Growing Hops in Key West, FL....
: Northern English Brown
: Mounds Bar Imperial Oatmeal Stout, Sweet and Sour Wit, Imperial Rye Cream Ale
: Steamboat Willy Cali Common, Rye PA
: The HBT Sweaty Fat Guys Cigar club