Most will NOT hate you and the ones that do can easily put the headphones on.
I would speak to the person at the check in and explain the situation. They might be able to give you the seats with more legroom, so that both can sit on the floor and play when the seatbelt sign is off.
I've done massive, long haul flights with my 2 from the age of 10 weeks. I give calpol to set in before descent as it seems to prevent the ear pain.
Obviously, I don't know the extent of your DC's ASD so that would change things but here are some general tips:
Let them crawl/run around as much as possible before you get on the flight. Change nappies/so toilet trips immediately before boarding and if recently potty trained, put a nappy on for emergencies. Make sure you have packed spare clothes for all of you incase in case of accidents.
Some recommend boarding plane last but I never do, I find earlier helps so that someone doesn't use all the overhead space and create more problems.
Take dettol wipes on the plane and wipe down everything, like armrests and trays. This may seem crazy to someone but they're covered in bugs/viruses and eases some of the anxiety when your DC might start chewing the arm rest or licking the window (been there).
Do not skip nap times in the hope that they will sleep. It will just make things worse.
Have a really organised hand luggage for all of you. I made simple games like button in a jar (get a small Tupperware box and cut a slot in the top and fill with big, coloured buttons. Little kids love spotting them in and it kills 15 mins. Buy cheap buttons so doesn't matter when they're dropped).
I went to Wilkos and bought each a big cosmetic bag and filled it with cheap, party bag type toys. I kept hold of these and took a new toy out every time they were about to kick off.
Pack lots of snacks. Healthy is better for obvious reasons but whatever works for your kids and keeps them happy. Don't pack anything that is an obvious choking hazard.
iPads with their favourite movies and games already downloaded. Earphones if your DC can stand them.
Ask for cups of ice when the hostess comes round. Kids love playing with and chewing on the ice. When cups are empty, use them for games like guess the cup and draw faces on them. Puke bags also make useful puppets!
Stickers are good. I let them stick them anywhere they went and just remove them before the end of the flight. Letting them stick them to my arms and face seems to amuse them for a while.
Take lots of dummies if they have them and lots of bags for dirty things. I have gone as far as to label them 'clean' and 'dirty' to make things easier. Plenty of baby wipes!
Good luck and make sure you go with the mentality of being at work. You aren't going to be able to have a drink, watch movies and read a book like the other passengers but treat it like a shift at work and tell yourself that you will relax afterwards. Don't worry about other passengers, it is what it is