I started laughing. Everyone invited to this momentous Coronation will receive a beautifully designed invitation that will be a true memento.
The Sussexes receive an e-mail..."Are you coming or not? We need to know how many folding chairs are to be set up in front of the doors at Westminster Abbey. We also need to know if you will be attending the Reception/Dinner...your table will be either at the exit door or next to the kitchen. Sorry, space is at it's limits. Please e-mail your acceptance or regrets within the next 2 days."
P.S. If you should attend, we ask that you have arrangements made in advance to remove your remaining junk left from Frogmore Cottage before arriving in the UK. We need the space to be vacated ASAP after the Coronation, time is of the essence."
Your Loving Father and Stepmother.

To be serious, I figured they, more than likely would receive some sort of invitation. When they were instructed to vacate FC "after the Coronation", it seemed as if they would be attending.