The Greeks, as my Greek friends have concurred, celebrate Easter as much as, if not even more than, Christmas. It's a festive time.
I would keep your schedule as is. I was with a tour on Easter in Santorini. We were having dinner at our hotel and was told it was a buffet. Great, i thought, with a buffet there had to be lamb. No lamb. I wasn't happy. If I was on my own, I could have made reservations somewhere to have the traditional dish for the day. (Roasted lamb on a spit.)
I don't know how adventurous you are, but, I'm going to suggest getting to Greece a few days early and going to one of the islands. The attitude of the people on the islands is different than the mainland. They seem to be more relaxed, happier, and more festive. I was on both Crete and Santorini on Easter weekend and everywhere we went it seemed the people were happy. They would fill the outside seating areas of cafes and restaurants talking, laughing, enjoying the sun and having a good time.
They were not sitting outside because of Covid. They were sitting outside because of the weather.