It has been a while since I've been on here, seems that I've come back just at the right time
We do full immersion and baptize in the name of the Father, Son, and Holy Spirit. I believe personally it is more than just a proclamation of faith or a mere symbol though, but that it regenerates body, mind, and soul, and God's grace works through it. Is that to say that a baby who isn't baptized and dies a tragic death can't be saved? No, of course not. God can work other ways too if need be I am sure.
However, this is the means by which He has given to all of us. It is the regenerative power of baptism that is the reason we baptize everyone as early as possible. God's grace is given to all, regardless of age and capacity to reason. Otherwise, those with mental handicaps or severe physical disabilities would not be able to be baptized either if we limited it to only those who could decide to do so by their own reasoning.
The public and/or private proclamation of faith comes later, when the person grows to the age of reason (if possible). They can then decide what to do with the gift of God's grace for themselves. Baptism does not force one to hold on to God's grace if they do not want to, just as God will not force Himself on anyone if they do not want Him.
“If the history of the 20th Century proved anything, it proved that however bad things were, human ingenuity could usually find a way to make them worse.” - Theodore Dalrymple