Frankly, I think that Google Scholar and just plain old searching on Google (just type in independently, each of the 3 areas of interest), will take you to an initial treasure trove of references, programs, etc.   From there, you might want to refine your search to more specific aspects of each of the 3 areas of interest to you. 

I fund the American Child life Council website (https://www.childlife.org) to be en excellent source of information and resource for activities aimed at helping children cope in stressful situation, illness and hospitalization.

In addition to Hiram suggestions, I'd add a search in Amazon.com. For instance "play therapy" returned  1,425 products.

Additionally, you may be interested in this article of mine: 

http://www.tandfonline.com/doi/abs/10.1080/02739615.2014.948163#.VaumzXikVZU

Michele

I fund many papers on research-gate by using your key-words; so RG is a very good source, too. Google scholar shows 149.000 results using your key-words. Is there something special you're looking for?

Best regards, Melanie

The 2 play instruments...The Children's Play Therapy Instrument (CPTI) for children with a clinical diagnosis and The Children's Developmental Play In strument (CDPI) offer mulitidimensional tools for the observation and assessment of children at play.  They have recognized reliability and validity.  As author of these instruments I train researchers and clinicians internationally in their use.  Saralea Chazan

I am not aware of anything related to art therapy and children but Bella has a great paper on art therapy and "stuckness".   THE TAO OF STUCKNESS: A HEURISTIC ART-BASED INQUIRY INTO FOLLOWING THE THREAD OF THE STUCK EXPERIENCE by Kim Bella. She might be a resource person who may be aware of adult therapy information that is related to children.