@Auntiegaston
I’m not sure I’ll ever change my view on my wedding as I was doing what I thought was right at the time. I understand why MIL was hurt but my mum was also hurt she couldn’t come. But that was 10 odd years ago.
Don't. I'm not sure why you've had a number of responses suggesting you've commited some gratuitous, barely forgivable offence by having the wedding of your own and DH's choosing and only a couple of friends present. But I don't set the store by weddings that many MN members do, so I wouldn't necessarily see why it's so 'hurtful' to marry quietly in this way.
My DH and I married in Italy with only one couple we are friends with and their two children present. My dearest childhood friend, who I've known since I was four, wasn't there. My brother, to whom I'm very close, wasn't there either. And my mum is dead. We told others of our plans shortly before we left.
Big parties have never been the way DH and I celebrate. We are fairly unconventional. We don't stand on ceremony. We like informality, we don't like attention, and an identikit wedding that 'others expect' would have been anathema to both of us. Anyone who knows us, or even knows the remotest thing about us, knows this. The issue arose, I think, because DH's family barely do know him. He left home at 18 and hasn't been back. His mum contacts him (and our DC) all of three times a year. This considered, it shouldn't have come as a surprise that it never even occurred to DH or me that anyone might mind.
My family, my friends, all our mutual friends, were delighted for us. Sister-in-law went on the attack because we'd dared to do something unconventional without having it sanctioned by her. MiL said nothing, but according to SiL she was 'very, very upset'. In the circumstances I don't see why. It was DH's choice even more than mine, but of course being the woman I am 100% at fault. When are we ever not?
All this said, if I could go back in time I'd do exactly the same thing again. You had your wedding the way you wanted - the way that was imposed on you because of your child's SEN - if others choose not to understand that then that's on them. Now let her get on with hers. You don't have to prioritize her when it comes to making your own plans but that seems an inevitable consequence of the nature of your relationship in general, not the wedding per se.
Drop the rope and let DH deal with her.