We are guilty of letting our son have a go at his Nintendo DSi every time we are on long train journeys in Japan. That's the only way to keep him from the need to run around or bother other commuters. Raimie can be such a nosy boy when nobody is paying attention to him. Though once you, a stranger talked to him, he'll clam up and hide behind his Mom!
But he is still not allowed to play it while we were put sight-seeing or while walking around! Only on trains or while in long queues so that he won't get too bored or fidgety. I totally wonder why some parents let their children be occupied with whatever handheld games they have while walking around. It's better to sightsee or just be aware of the crowd than being engrossed in your own world, right?
I wish he would want to read books once in a while, but oh well. No such luck yet!
What's your secret to keeping your child/children happy while on a vacation?