Tammy,
Although chronologically 50 y.o. isn't considered childhood anymore, my ITP in 2010 resulted in six weeks of hospitalization because I did not respond to any of the multitude of drugs and IV-IG offered. I don't recall them all, but I do believe my hematologist tried about a dozen, the one I had some success with eventually was WinPro.
It was very traumatic and frustrating, for weeks not responding to attempts to get my platelets up. I'd been swallowing blood from a nose/sinus bleed for several weeks; IV's attached 24/7 (or nearly so), my super-charged mind racing on steroids.
I felt so hopeless, and really thought I'd never "clot" again!
Reading here about all the different experiences and outlooks does help me understand more of the scope and variations in treatments. One thing I've learned is, doctors are more concerned these days with symptoms rather than strict interpretations of platelet counts.
For example, I just assumed anyone with low platelet counts (3,000 5,000 12,000) was hospitalized; that is not necessarily true, one has to take bleeding symptoms and other factors into account.
Read and ask a lot of questions; there are a lot of different experiences related in these threads! But remember you can't worry your son's way to health, so be strong and healthy for him!