I'll be at the concert as well. Are you staying downtown?
The best place for dinner downtown is on East 4th Street if you like meat. Mabel's BBQ is owned by world-famous Michael Symon (The Chew TV show). There are several places there for eating or drinking. For breakfast, Yours Truly, is the best (Playhouse Square). Hotel Cleveland may be fun...it is a classic old hotel that just reopened after a massive remodel. Another great place to eat is Johnny's Downtown. I'd take care to the East Bank of the Flats and go to any place there. It is on the river and is kind of "Cleveland" as you sit outside and enjoy the waterfront. I like Collision Bend and The Lakehouse there.
My favorite Italian is a bit out of the way but is Bruno's on West 41st but you can go to
"little Italy" and enjoy a dozen great restaurants there (on the east side. Its a bit of a longer drive (East 117th area) but has great restaurants and bakeries. Fun to just walk around, get a drink, then a dinner, then a desert.
Let me know if you have more questions. If you tell me where you are staying I can be of better help.