Dear blessed husband,
When I tell you that a dear friend has invited a whole bunch of families (including ours) for Mother's Day dinner, you would do well NOT to say "That's okay because the time for the dinner reservations wasn't very good anyway."
This only serves to confirm that for ANOTHER year you didn't bother to do anything about Mother's Day until a day or two before the event, when all the normal dinnertime reservations have been taken and all that is left is 4:30 or 7:30. If you had kept your mouth shut or only said that you would cancel the reservations that you made, I would only have my suspicion that you delayed too long, not absolute proof.
Mother's Day is clearly marked on the vast majority of calendars in America. This means the date is available to you in January, if not earlier. Restaurants book reservations well in advance. There is no excuse. Get your head out of your butt and act on things in a timely manner.
Ditto Christmas and my birthday.
Your blessed wife