In February we survived a 5 hour delay in CVG thanks to a very nice play area in terminal 1. Clean, fenced in with a white PVC fence and had various climbing structures on a rubberized floor. It's not very well advertised and seems to be hidden at the end of the terminal (by the Delta Crown Room). I espcially like the fenced area as it helped keep the ball my kids travel with "in" and non kid people out. It is amazing how many times I have found a so called "Kid" area being used by a non kid person for a nap. No biggie, but please spare me the dirty looks when my kids do start playing!
LAS has a nice play area as well - a bit sparse and can run a little dirty at times, but still - it's a great place to let the kids run off a little spare energy without interfering with travellers around them.
Feel free to contact me if you'd like. pm me for contact info.