Hi Fana,
I am sorry to read that you have to face this with your son.
The outcome for children with AA is much better than adults. The current standard of thinking is to go directly to BMT for children with matched sibling donors. If no match sibling exists, then you would go with ATG. The BMT survival rate for children under 20 with matched sibling donors is very high and offers the chance for a cure. ATG is not a cure.
Of course, with children it is imperative to check that the AA is not an inherited form of the disease (like Fanconi's etc). Be sure that your son is being seen by a pediatric hematologist with expertise in this rare condition and that they are ruling everything else out that it could be. Where are you from?
I would encourage you to check out the excellent AA videos at the AAA&MDSIF website for information from experts across the US:
https://live.blueskybroadcast.com/bs...T=944&CAT=1031
Also, here is an excellent article by Dr. Neal Young about how AA is treated:
http://bloodjournal.hematologylibrar...ent/120/6/1185
I wish you the best!