Severely disabled ID + car discount

Hello municipality, I think to have heard that the car companies (Audi e.g.) give a customer discounts (my 19%) via a disabled ID card. Is that right? And who can buy a car? Actually only people who are “businessable” – say 18 years and older. Background of the story is – my son, who will soon get a severely disabled ID card and we will soon need a new or different car because of his illness situation. From an acquaintance ha I have heard that you can let a car insurance on your children?!? But how about buying a car in general? And please don’t discuss any rafflery about percentages in this matter. We are punished enough … Oh yes… my son is going to be 3 years in April and can’t walk. Thank you for your help Greeting Markus