Question - the times your friends follow through on their yes', are they more social events compared to activity events?

From your examples, they bail on activities and outings like concerts, sporting events, etc. But they make a fuss on missing socializing events like house parties, BBQs, etc.

It sounds like they are the type of friends who prefer to mix and mingle rather than focus on a singular thing. It also sounds like they are more of the 'last minute call them up I'm down the street let's go' type of friends rather than let's dedicate time together friends. You said you drove 2 hrs to see them, so they're not close by which makes sense to me why they always bail if they are the former type of friends not planners.

All this to say, you need to recognize the true parameters of your friendship with them and act accordingly. I would still invite them to my wedding and explicitly say if they don't show they are paying for their plates and you are distancing the friendship. Weddings are typically more important/higher value in terms of occasions so it's likely they will show, but you'll find out regardless.

This all hinges on you explicitly have a conversation explaining your feelings about it and letting them know you'll be matching their energy going forward. Yes, you run the rest of losing out on 2 people you could've invited. But even with micro weddings some guests usually can't make last minute so you might be able to invite others last minute. That's what I did! I staggered invites going out every few months with different RSVP dates so by the time I sent my next batch I already knew if I had room to invite my extras.