This is a great three day trip but you could do it in two.
Day One: leave early and take I-64 to O'Bannon State Park near Corydon IN, about a 3 hr 45 min drive. O'Bannon has at least 17 miles of great singletrack with several fun flow sections.
Corydon looked like a cool town so you could just eat there and head to Brown Co. or stay the night. But Louisville KY is just up the road a bit and has all the food and drink you'd expect in a college town.
It's about 2.5 hrs from there to Nashville IN/Brown Co. State Park. We forged ahead and stayed the night in Nashville. But to do justice to O'Bannon and to have a more relaxed trip next time I'll stay in Corydon or Louisville the first night.
Day Two: either way get on up to Brown Co. State Park which by now probably has more than 30 miles of premium MTB trail. Haven't been there? Go! go now!
Nashville is all about tourism so there's lots of places to stay. Not a lot of places to eat but Big Woods Pizza and the brew pub are good. Columbus IN is a good option for a wider selection.
And if camping is your thing O'Bannon and Brown Co. are very well run state parks. (If you camp you'll save the vehicle fees, see below)
Day Three: Knock out a quick ride of your favorites from the day before and head for home via I-70 about 4.5 hrs. You'll pass through Bloomington IN on the way if you want to grab something to eat or Terre Haute is a little farther along just off the interstate.
Finally, consider buying $20 season passes at the O'Bannon gate which is good at all Indiana State Parks and goes to the trails. You have to buy a day pass anyway for $5 for each bike rider (plus $9 for out of state vehicles which goes to the park). So you'll enter the parks three days this trip and having the card gets you through the gate quicker. And if you go again in the same year you'll save a bit. Plus did I mention the $ go to the trails?