In case you haven't checked the Nov hours that dropped a few days ago, MK closes at 4:30 on Nov 17. That along with the party days will make MK VERY crowded on non-party days that week. Just thought you might want a heads up for planning purposes.
I believe you said your tickets had already come in the mail? What kind of tickets did you purchase as most do not come in the mail anymore. Anyway, I'm doubtful that you could exchange these, but it never hurts to ask. It will definitely take a phone call when/if free dining opens up.