Should baby mama come to the wedding?

I'd love to hear everyone's view on my slightly sticky situation.

My fiancée and I live really close to his ex, the mother of his two children. I now know her pretty well and it's all been very amicable from the beginning but unfortunately she's just around a little too much for me. As nice as she is, she is extremely dependent on him, not only financially, but emotionally and socially. As I like to call her kind, she is ‘A wet Flannel’. (She comes from a lot of money and has never really had to work) After we got engaged she messaged him saying she missed him as a friend and as much as she liked me she was starting to resent me because I was 'always there' (by always there she meant in my own house where she often invites herself in for cups of tea when dropping off/picking up the children or to see our new decorated bedroom ect 🙄 I stay away as much as possible because of that very reason) She asked him if he could make time for her and hang out watching movies and getting take aways like they use too “without me there” 😐 (Not that we do it together!) That's a complete other story!

Anyway, here is the catch, my fiancée is slightly autistic and finds social events painful enough as it, let alone the idea of his own wedding with all eyes on him. He has no siblings and both of his parents have passed so we're having a slightly unconventional wedding anyway as I don't want it to be a constant reminder that he has no family. Hopfully it's going to be a really chilled and fun day. I'm not letting my dad walk me down the Isle, they'll be no special speeches or first dances because I feel it's all a reminder that his family are not there with us.

So it's come to the wedding guest list, and he puts his Ex's name down because 1) His children need looking after during the day and 2) H

e thinks she will be upset that everyone else is going and she is not and he doesn't see the issue as there are no hard feelings between them.

Because of his autism, he is really struggling to see why I would find this uncomfortable and not that it should really matter, but why it makes my friends and family also uncomfortable having her there.

Before anyone says it, I 100% know in my heart he has no feelings for that women so I'm not concerned about that at all but I just don't know wether to let this slide or put my foot down with it. I think it’s causing him more stress to not invite her than it would for me to have her there but I just think all guests are going to be so uncomfortable and shes probably going to hang around him all day the way she does at parties/gatherings.

People of Glow, please help me!