Looming face to face assessment with Atos

Hello,

I am a new member here. My son has ASC and Sensory processing disorder and Hyperacusis which is an acute sensitivity to Sound. He has recently turned 16yrs and as his appointee been advised that he will no longer get DLA both at higher rate (mobility part was awarded at Tribunal) for indefinite and I have applied for PIP on his behalf. I have just received a letter stating that there will be a face to face assessment at our home during the day when he will be at school. I am not sure what to do and also my son suffers from acute anxiety due to his sensory disorder. He cant walk on the street without having a meltdown and notability car has been a God send. His understanding is not typical as well and just telling him there will be an assessment got him very anxious already. Will they talk to my son though me or will the questioning be directed to him? DWP already recognized me as his appointee so not sure why they would put him through this highly stressful situation. Please can somebody advice me on how to proceed?
Thanking you in advance.

Thank you for your reply. My son is capable of responding but have limited insight into his condition if any. He will tell you when asked that he can buy items with money but he will not tell you that he will not wait or expect a change for his money or how much change he should get back. He needs me to be able to explain in detail how his condition affects him and will the assessor take my word for it?

My son had his face to face assessment today. I did say to the woman that because of cognitive/mental difficulties, my son may not be able to answer her questions.She still wanted to talk to him and didn't checked my son's answers with me. The woman asked my son his date of birth, the date today, the year we are in, and some adding and subtraction questions (10p +30p, 50p - 5p etc) to which my son answered correctly. iIf you give my son £20 and he bought something for 20p, he would not wait for change or know how much change he would get. I am so afraid that this is going to be taken as he is able to function the same way when buying goods in a shop which my son has never managed to do before. My son asked her if she was going to take our car away and she didn't answer. I am so anxious I feel like throwing up. My son was asked to read a sight test paragraph which he did. He can read but understanding is not there. He was asked to touch his nose, mouth and forehead which he did but I do not understand what this mean and whether because my son was compliant that PIP are going to say he doesn't need the same level of help he is getting now. She asked my son "do you cook?" and he answered yes but with my mum and teacher's help. Can you please tell me how long before we hear back from them now that the assessment has been done. And is this the standard of questioning aimed at autistic people?