Get back on the phone, get a form for CA(see note about earnings)and get a form for mobility component!
I must admit, I have dd's mobility forms still to fill in, she was 3 in October! I may actually get round to it soon too!! Her care DLA expires this October so I will have all that to look forward to!!
According to the DLA note a child of 3 can only get the higher rate if any of the fiollowing apply;
1.cannot walk at all
2.only walk a short distance before feeling severe discomfort
3.effort of walking could threaten their life
5.deaf and blind and need someone with them when they are outdoors(!!!)must have a large amount of hearing and sight loss but not necessarily totally deaf and blind
6.severely mentally impaired with severe behavioural problems and needs help with personal care both night and day
you might be able to get low rate mobility, I'm not too sure of the crietea for lower rate but she may get it. Sorry I'm not much help, I don't have much knowledge of Autism, Cerebral Palsy YES, Autism NO!!
I would just put the form in when she is 5 TBH. I mean you could try and get high rate mobility now, and see what happens, but if she doesn't get it, then just try in 2 years to get the low rate, it all helps in the end