Where are they staying?

Dancing? What type? Many tourist stop at the wild horse saloon. If it's before 6 and they are older than 18 then the girls could go there for line dancing...

Most music venues will not allow anyone under the age of 21 at night, before 7 they can go grab a bite to eat and listen to some music. Some even cater to the more indie rock or blues crowd.

Studio b tour? Ziplining and obstacle courses at Nashville shores? Hiking at Johnsonville state park? Centennial park snd the Parthenon? Frist art museum if they are into that. hockey game?

Hillsboro village area will be full of college kids (vandy) and has shopping, arts and some clubs that cater to both over 21 and over 18, shopping is there as is belcourt to catch an art film.

Just walking around broadway and the honky-tonk scene is interesting people watching,

What sporting event? Sometime there will be mini Fairs or festivals that pp up around the sporting events to grab more tourism dollars. They can be fun to check out.

Sorry I'm not more help. Not familiar with that age group that isn't a die hard country fan sneaking into the clubs here to soak up the amazing scene or seeking out the grand ole Opry, cm hof, dying to check out the guitar store or some venue where or so and so did this or that.