Get a grip.
For three days you are to concentrate on you. Pack, fly, have surgery, recouperate for a day, go home.
Your son will survive. All autistic children survive being away from their parents for 72 hours. He may melt down, but he will survive.
You don't need much more than a comfortable pair of shorts, a t-shirt, a nightgown and flip flops. Add some sweat pants, another t shirt, a comfy light jacket, your hairbrush, tooth brush, deodorant, toothpaste and eyeglasses if you wear them, a pony tail holder, your gas x strips, birth certificate, ID and you're done.
You can skip the make up and the hair implements. They have hair dryers, shampoo and conditioner. Dont' bother with jewelry or fancy clothes. They have broth and juices in the hotel. There's a Starbucks across the street.
Keep it simple and you won't have to worry about forgetting a lot.
Son needs clothes for three days. Meds for three days. Medical insurance card.
It's only 72 hours.