sorry just seen this thread
IN terms of DLA - you would be eligible for either a carer allowance or a carer payment. I get the allowance - bog standard so much a week and not means tested as dd1 has a disability but it is not severe. You would probably be eligible for the other one which is means tested but is more for those who have to care almost full time for their children iyswim.
My dd1 has down syndrome.
Just curious as to what sort of visa you are intending on applying for. I do know of a friend whose stepson had some disability ( can't remember what it was) and they had all sorts of hassles with it.
When your daughter turns 16 then she would be eligible for a disability pension and I think you may still get payment for caring for her.
info re carer payment here
there are other services attached so if you search around that centrelink site you should find out more.
It depends from state to state as to who provides the services etc.
WA disability services
Our health system
here
dd1 does not need a lot of equip - but some that she has utilised has been provided by disability services.
WW education department
Our dd1 had dual citizenship - born in the UK but she had australian citizenship by descent. My english dh came in on a spousal visa. No need to apply for dd1 then.
schools and therapists can vary from city to city and within cities. I am far away from WA and so can't comment BUT i imagine it to be like anywhere - good and bad.