When I left my church after a 28 year pastorate, the congregation threw me a big party. There was a tent, catered lunch, and testimonials. Everyone in the church was invited. It was great and I appreciate it but for me something was missing.
I think a special service or ceremony was needed. A ceremony acknowledging the end of the relationship and the beginning of something new for all of us. Besides music, hymns (my favorites, of course), and prayers, there might have been a sermon on change. Perhaps an official pronouncement of the end and an exchange of symbolic gifts. And a special blessing for all.
And then the party!