The downtown area and the Opryland hotel come to mind. Music Row isn't anything that interesting...it's just where a lot of the big record companies and recording studios are located.
Downtown has all of the little honky-tonk bars along with some excellent rock bars, Hooters, Wild Horse Saloon, Hard Rock Cafe, Buffalo Billiards (your DH and friends would probably like the last one), souvenirs shops, cigar bars, etc.
Hilton Suites, Doubletree (Hilton), Rennaissance (Marriott), and Courtyard Nashville (Marriott) are all within walking distance of the above-noted attractions on Broadway and 2nd Avenue...also called "The District." Hilton Suites and Courtyard will probably be the less expensive options of the four.
Opryland Hotel is a full resort all in one place. There are several stories tall atriums full of tropical plants that have to be seen to be believed. Tucked in the atriums are several restaurants and bars. Also, within walking distance of Opry Mills Mall. May not appeal to your DH and friends, but worth a look at their website anyway. Even us locals like to go there for a walk through the atriums and have a cocktail or coffee. The Grand Ole Opry is also on the grounds of the Opryland complex, but unless they plan on going to one of the shows, it isn't anything more than a big landmark.
HTH! You're welcome to PM me if you need some more info. Hopefully I can provide it.