tbh, Kids being excluded from things is also a life lesson (all things well with them and not those dealing with SN or a disability, I'll get to that)
Its one of those things kids will have to learn sooner or later. Not always being invited to a party/sleepover/play date or whatever is going to happen. It doesn't mean people hate them or that they have done something wrong. It just happens.
It can also be very damaging to kids to coerce them to invite everybody to a party. You are effectively encouraging them to be 'friends' and make do no matter what the other child's attitude is. We need to give children far more credit than we do so if they say I don't want A,B and C there. Do that, let them explain why and even if you don't agree be there to help deal with whatever happens after. 99% of the time it will be fine and kids tend to forget after a week!
Also, If a parent makes a big fuss about their child not being invited to the party... Meh. My party, my rules.
As for SEN kids and those with disabilities it really isn't unreasonable for all parents to make an effort to include that child. Even if it means the SNs child comes to the party a little bit earlier to spend time with the birthday child and leaves before it gets rowdy. That's still inclusion! Write a specific invitation for the SN child and their parent. Give a rough list of what you plan to do so they can prepare that way the mum of the SN child can get in touch and explaining if anything will be an issue, if there will be triggers for meltdowns or even if she wants to come too. It just shows you know there are difficulties and you give a damn about making it work.
The boy that showed up to my child's party was also SNs and the mother was incredibly grateful I had made the effort to a) not have any balloons (the bangs scared him) and b) make a birthday cake that was dairy free. It wasn't difficult. It just meant I had to grate a ton of butternut squash for the cake and make decorations from paper instead.
Now if everyone else had bothered to show up I reckon it would've been a grand party. Instead we raced to see who could open the 20 layers on the 2 pass the parcel presents I made. Chased bubbles from the prizes, flew a couple of kites and played in the park.