Give me ideas please! How to handle a family schism for wedding?

My FH's side has a bit of a complicated family. His grandmother and grandfather are divorced and not so amicably. They can't really be in the same room as one another. I want to be as accommodating as I can, but I'm not sure how to make sure both family sides feel included without having essentially two wedding and receptions. They cannot/will not be adults about it, if we invite the GMA, no one from the GPA's side is allowed and vice versa. I've only met his GMA once and know much more of his GPA's side. However, his GMA did send us money for our engagement/wedding already. I have a strong belief that it is extremely rude to not invite someone who's financially contributed to your wedding, but what do I do in this case? We need the help, but I'm at a loss as to how best to make everyone happy.

Currently I have two ideas... Option 1 is we invite everybody and have a note in the relevant parties invites that says "X is also invited. Please be civil about it if you want to come" in nicer language. Option 2 is we invite the Gma's side to a rehearsal dinner the night before and the formal wedding day-of but not the larger reception. However, that likely means lying about the larger reception to some degree and that doesn't feel very good.

I'm not sure what's fair to me and what's fair to them and if there's a compromise but I'd love some feedback from anyone who's been through this before or has a similar situation they're trying to handle.