We mailed out change the dates- the lady who did our invites did a round for free. We also did a Paperless Post invite for our minimony. I would definitely send something out in the mail for your big ceremony though.
I sent out postponement announcements (we postponed to 2022), and will be sending Change The Date cards when time gets closer, along with new invitations. Those that previously couldn't make it to your original date, may now be able to make your new date, etc. Definitely send out new invitations!