But you don't know that you were only invited to provide a ride for your dad. Isn't it possible that they realized you're not comfortable being tacked on to your dad's invites and rectified it this time? I understand that they have a closer relationship with your dad than with you, but that doesn't mean they'd happily never see you again if there was another convenient (for them) way to get him to events.
I get the impression that this isn't really about the invitation. I think you resent the combined attitude of these relatives and your dad that of course you'll bring him, as if you have nothing else to do or you owe it to him or whatever. Maybe they want to see you, maybe they don't. It's hard to gauge because every invitation is All About Dad. I understand that. If you don't want a relationship with them at all that's okay. You can decline this and all future invitations until they realize and stop inviting you. What happens with your dad will be up to them to figure out.
If you do want a relationship, keep an open mind and go. See how you're welcomed, if anyone greets you and makes time to chat with you. Take the initiative and sit with someone, start a conversation, see how they respond. If you leave feeling good then go again, if the day confirms that nobody has time for YOU then you'll know what's up. At least then you can decline future invites without the stress!