I will be put things in a little different context, so I hope no one takes offense.
Orthodox take the Bible way more literally than many protestants do. Baptism being one example.
When we're baptized, we are baptized (ie: united) into the death, burial and Resurrection of the Lord Jesus. (Romans 6:3-5) For us this is a literal event. We literally die with Christ, and literally rise with Him, although we do so Mysteriously. (hence the term Mystery)
Baptism joins us to the body of Christ which is the Church, and we put off our old man and put on the new man.
The age of person isn't relavent. For Christ said, "suffer the little children to come to me, and do not forbid them. For such is the kingdom of heaven."
The way we see it, is by not baptizing infants we'd be denying our children the Mysterious union with Christ and entrance into the Church.
Christ said, "Unless one is born of water AND the Spirit he cannot enter the kingdom of heaven." John 3:5
Yes, we have to be born of the Spirit, but this happens in water baptism. At a baptism its not "just" water...it LOOKS like just water. But we walk by faith and not by sight. We "see" someone being dunked in water, but at the same time, thingd happan that we can't see. At a baptism God uses material things, in this case water, and unites His Holy Spirit with the water. So at a baptism, at the invocation of the Holy Trinity, a person is being born not just of water, but water AND the Spirit.
John's baptism was just a baptism of water. But Christ's baptism is a baptism of water AND the Spirit. Its a simultaneous event. Where we are born from above. And Mysteriously die and rise with Christ, shedding our old man, and putting on the new. However, the grace of being born from above doesn't automatically make us perfect. We must be taught, and nurtured in how to USE the grace we receive at baptism.
As for baptizing infants...well obviously you believe Salvation is a free gift from God right? You believe there is nothing we can do to earn and achieve any merit to be worthy of Christ's sacrifice. If this is true, (or at least its the baptist motto) then why do baptists say we must 'achieve" understanding before we can be saved?
For low church protestants there is a certain amount of 'knowledge' one must gain, or achieve, before being able to be saved. Theres even a saying we must "come to a saving KNOWLEDGE of Jesus Christ"
To us, this doesn't make sense, for we can NEVER gain enough knowledge to acheive salvation. We dont even have the ability, as finite beings, to fully understand all of what Christ did for us.
For us, we can't DO anything to earn merit to be joined to Christ. This is in fact why we baptize infants. For as an infant, at baptism a person is freely receiving, without any merit whatsoever, the gift of being born from above.
An infant receives God's gift FREELY. In this way, God's grace, the Mystery of Illumination is truly a free gift, that is bestowed upon an infant, not earned by logically accepting what Christ did. Christ even said we must receive Him as a 'little child' (but in the Greek the context is that of a child less than 2 years old) so we're simply doing what He said.
An infant may not understand what is going on, but then again, do adults truly understand whats going on when they come to faith?
Now of course, as the child grows they may later choose to leave Christ and go there own way...but to us, its better to raise them as a complete and full member of the Church of Christ where they can receive the Mysteries and hopefully grow in the Faith rather than deprive them from being in the Church.
This probably wasn't much help as I'm not really thinking clearly today....so I apologize if I've only confused you...
In Christ, Chuck