I recommended walking on the map above and almost recommended Church Street Park. I didn't because it's small and some people wouldn't be thrilled by outdoor connect four and chess and maybe some homeless people, but my kids love those kinds of games and rarely get them at home. It all depends on what you do in your everyday life and what you think a vacation is.
They do have live music on Friday at 4:30, though. Older adults could go into the Nashville Public Library for air conditioning and the Civil Rights room:
https://library.nashville.org/research/civil-rights-room
It's also again walking distance from downtown hotels, depending on your tolerance for walking. More like a half mile than 1.5-ish miles like the map is.