6yo DS has ASD, and we invited about 15 kids to his Y1 party this year. Most came.
He had a whole class party last year in reception at soft play, and lots - but not all - came to that.
I was dreading DS's party this year. But he was adamant that he wanted one, and so we went with organising one that fitted his requests, and that we thought we could manage. DH found a great entertainer. DS didn't want soft play (and he doesn't do well in soft play). We had a much more structured approach - although it had plenty of over-excitement - than most of the parties DS has been to.
We found the party itself pretty stressful. BUT. DS had a whale of a time, and not a single issue. Some of the other DCs were a handful, but everybody survived, and DS had loads of happy feelings. He was on cloud 9 for about a fortnight after his birthday.
So it was definitely worth it for us. After so many dark times, particularly over the past year, we will bear a lot to see our DS carefree and joyful.
I do find the school gate chit chat a bit hard - especially at the times when things have been most difficult with DS and I have felt like I had little in common with the other parents. Quite a few parents now know about DS's diagnosis, and have been very supportive. I get the impression that this can vary from school to school.
Do you have one or two parents who you talk to, who you could sound out about a party? It is odd, in my experience, for your DS to have had only one party invitation - although there is a bit of reciprocity in invitations, and if you didn't have a party for him last year, that might be contributing. With ASD, you do need him to have the opportunities to practice skills and be successful.