My wife and I have travelled with my son, now age 3, on several occasions. We usually try to take nonstop flights where possible (and affordable) to keep the total travelling time to a minimum. On the occasions where we fly to Roanoke to visit family, however, we prefer to fly DL through CVG. There is a simple play area on the end of the A Concourse of Terminal 3 near where you enter from the other terminals. It's got some indoor play equipment, a TV showing kids' programs, and some toys. It's nothing fancy, but it's a very welcome diversion when travelling to break up his boredom and to get some energy out.
Play areas are a great idea. It really is a relief to harried parents who are trying to hustle through a crowded airport with kids, bags, snacks, and whatever else in tow. I don't see very many of them in airports around the country, however. I imagine cash-strapped municipalities aren't very keen on the idea of a free play area in airport space that could otherwise be occupied by a rent-paying business. The play area at CVG seems to be in a spot that wouldn't really fit a business, except possibly another shoe shine or maybe a cart/kiosk kind of operation. It's a nice place to stop and let my son play a little, but it could be much better. The TV doesn't work all that well, and the indoor playset is the very small slide designed for children about 2 years old. While it's welcome, it pales in comparison to the play area in the food court of our local mall.
If I were to design a play area in an airport, I'd have two sections - one for bigger kids, say 5 and up, and one for younger kids. I'd make the bigger kids area like the playlands at McDonald's. And I'd scale it down for the younger kids. Ban shoes, food and drink in the play area. And absolutely require parental supervision. You'd need to have a single entrance/exit as well to make sure the kids didn't wander off and get lost. Put a couple video game consoles in there as well, and an TV playing Disney Channel or PBS Sprout. I'd also make sure there was a bank of arrival/departure monitors as well, so parents can check on flight status. And it needs to be free - we pay for enough stuff at the airports these days.
I suppose an area like this would take away from revenue-generating space. But maybe you put it near the food court area and sell sponsorship rights - the McDonald's Playland at Anytown International Airport, or whatever. I think this would make parents more comfortable flying with kids. And frankly, it will make other travellers more comfortable, too - since the kids will be playing in the play area and not running around by the gates.