The only real solution is, of course, proper inclusion, respect and reasonableness at all times. Sadly that is pie in the sky, for the most part.
I have 3 dc. All have ASD. Only dd1 'needs' SN sessions, the other two can generally cope in standard sessions, unless they are really packed.
BUT, most of the time, there is only me to take them out and about. So we cannot go to the standard sessions, because I cannot take dd1. If/when we go to the SN sessions, often they are fairly empty, meaning dd2 and ds do not have a grea time, as they have only each other to play with. They would greatly benefit from having a couple of considerate NT families around (as would I and dd1, as then I would be able to concentrate on helping dd1 more too).
The key, of course, is the balance, as I posted earlier.
But then, what suits me and mine doesn't necessarily suit others, which is what makes it even harder being a SN family, at times - I get well meaning friends telling me about the sessions, not realising that it can sometimes serve to make dd2 and ds feel even more isolated, and doesn't necessarily work for dd1 either if there is no one else around for her siblings to play with.
Sometimes, a lot of facilities would generally benefit from severely limiting numbers, with a sign up rota/maximum time to stay, as then a lot more peop,e would get a lot more benefit out of it all.