What the visit is like depends a lot on the show. People often praise the wooded setting and sound, but busy concerts can mean slow traffic getting in and out, especially after the performance. Give yourself time for the drive and walk from the event lots, and note where you parked before heading in.
For Cleveland Orchestra shows, the Lawn is picnic-style: the venue currently allows picnic food and blankets, with short-legged chairs. Rules can differ for other events, so check the details for your concert. Ramps, wheelchair seating with companion spaces, and accessible restrooms are available.