I would absolutely recommend going to the Kravice waterfalls. They are very lovely and every child (and adult) will love the visit. There are two cafes, where you can grab a cup of coffee or a drink. There are also toilets and “rooms”, where you can put on your swimsuits. You are able to swim in the small lake and to climb close to the waterfalls and “touch” them.
We did Mostar and Kravice on the same day. First Mostar to see the wonderful bridge and then Kravice in the afternoon. We returned home pretty late in the evening. It was quite a long day, and I guess some would prefer to visit Mostar one day and Kravice another day. But I think it was nice to get refreshed and swim after a very hot day in Mostar and on the road. Even though it was a long day, the kids enjoyed the day very much as well.
I think it’s worth going the distance just to see the waterfalls. Especially if you have kids that don’t have the patience to sit in a car for hours, so I guess it depends.