Ooh 12 months old? Well you have a steep hill to climb for DLA.
So, DLA for your DS is going to really depend on what his care needs are.
The Decision Maker is right, all children of 12 months need a great deal of care. So what you have to do, is to demonstrate that despite this, your DS has more care needs.
Giving specific examples, if you said 'DS needs constant supervision', the DM would be quite right to say 'show me a 12 month old who doesn't'.
If you say 'DS wakes frequently at night', again, no dice, they often do.
But, if you are saying 'DS wakes frequently in the night because his breathing is laboured, and I need to spend an hour giving him physiotherapy, or doing leg stretches, or positioning and suctioning, etc., then that is different.