Everyone reserves the right not to go to your wedding. As much as you might want them there, they simply don’t have to go. They can do the best they can to try to attend, if they’re super close to the couple, but if something else comes up you cannot blame them. It might seem like the most important day of the year to you, but to other people it can be a big financial and time commitment. This is especially true when you’re asking them to spend a lot of money on your big day (or the events leading up to it). 

One thing that’s definitely not okay is to be vindictive about your wedding invitations. As a rule, if you invite someone, you don’t really get to disinvite them. Unless something egregious has happened after you sent that invitation, you kind of have to stick by it. It’s just the rules of common sense.