If you go to Wimberley, you can take kids to "Pioneer Town".. The name pretty much sums it up. You could also take a scenic run up the "Devils Backbone" aka 32. There is a nice picnic spot that overlooks the valley, then you could come into Wimberley and go down river Road to 7A and Pioneer Town. There is also a Zip Line in Wimberley that is pretty cool.
If your a big Jeep guy, you could make an hour or so trip north on 281 and go to Hidden Falls Adventure park to do some wheeling. Google them up!