Mum making us choose her or Dad

Will try and make the context as quick and simple as possible.
Me and my fiancé both come from separated parents. All happily remarried apart from my mum who has a long term partner.Both our dad's cheated on our mums so not amicable splits, however mine was before I was born and OHs was when he was 14 so we are talking over 30 years ago.
We've been engaged since 2019, but apart from money, the only other thing stopping us is OH's mum who has said she would not come to the wedding if we invite his dad.
My mum has said the same however I know deep down she wouldn't miss it, she attended my sisters with him there so I know this.
With OHs mum it's different. She will not come. This akes me so sad because we really want her and OHs stepdad there.
But we can't not invite his dad.
It's so depressing as it should be an exciting time for us but been put off for 5 years because we just can't make the decision.
Any help would be appreciated x