Take the kids to Krause Springs in Spicewood late morning. Then drive another 30 or so miles up 71 to Llano for the best west Texas style BBQ at Coopers in Llano. On the way back hit pie happy hour at the Bluebonnet Diner in Marble Falls.
If you have kids and want unique I'd go to Gourdough's. They have food but I've only had the donuts. They are awesome and chances are you've never had anything like them unless you've had it at a state fair.