Hmm, maybe a bit of personal experience may help.
We initially went through our paediatrician who is also a cocklear (sp?) surgeon who works a lot with deaf children . . . he was more than happy to have extra helpers. He, in turn, suggested our services to other doctors in other fields.
This resulted in us 'babysitting' children while the parents had their support group meetings combined with body painting (the kids loved painting the ang-moh!) and assorted games . . . to having our kids play with children in cancer wards etc...
I would suggest fronting up to these places you have contacted and speaking with them face to face . . . it works wonders. (Much like charity work

)