Baptism by John the Baptist - including for Jesus - was by full immersion. The Greek baptizo means precisely this.
As with Jesus Himself, this was done at an age where decisions can be made and clearly must be your own.
Baptism-by-proxy is never taught in the Bible.
Infant christenings as a welcome to the Church are fine but should never be confused with baptism - and no, confirmations etc are no substitute.
Don't believe me? - Then read all relevant Scriptures yourself.
