Definitely the Parthenon in Centennial Park (near Vanderbilt University), for your non-history buff members while still offering you something of high interest. The statue of Athena has to be seen to be believed. (It's 40 FEET TALL!)
The Hermitage (Andy Jackson's home) should also be on the list. It's a little further out from the main city, but it's not hard to find and should be interesting to everyone.
Belle Meade Mansion, on the west side of town, is also an interesting visit. A Civil War era home, it also has ties to other aspects of history, being the homestead of the Harding family (relatives of Warren G
. not that they're proud of that
), and having hosted Taft. Plus, it's near Phillip's Toy Mart (just continue west down the road; it's on the left just past the first stoplight you come to), which has a great supply of scale models, model railroad stuff, and even some wargaming stuff (mostly GW and board games, but lots of 1/72 plastics, too).
For a day trip that combines history and shopping, come on down to Franklin, site of one the biggest battles in the CIvil War, and a darn nice town for wandering about (take the walking tour, which combines history and Southern charm!). Great little antique stores and boutiques, and good food, too. I recommend Meridee's bakery for lighter fare, and Puckett's Grocery. Oh, and Uncle Bud's if you love fried catfish. If you're there at night, take the ghost tour, which is very popular!
Oh, and in Nashville proper, plan to have breakfast at the Pancake Pantry near Vanderbilt. Expect to wait in line. Expect the wait to be worth it.
For dinner, head west, and keep driving till you come to the "Loveless Hotel and Cafe" (yes, that's the name). It's no longer a hotel (boutique shops instead), but man, is it a cafe! Southern cooking done right— try the country ham with red eye gravy or the fried chicken. And try not to stuff yourself on the biscuits and homemade preserves and molasses. You'll fail, but that's a battle you'll want to lose.
Enjoy the trip!