Well, that's why I said potentially open-invite. Assumption being, that if it's not, then said carpool would not happen. I am not at all interested in party-crashing!

How about this:

Should you decide to make this an open-invite, Grand Rationalist Gathering, then I will happily organize a carpool with other people.

Should you decide to make this a cozy celebration among friends, then of course I completely understand, and wish you best of luck!