If your kids are going to spend an evening clicking on web pages, the least you can do is find them something educational to click on. With this in mind, I bring you news of Seterra, a web site that teaches you geography while you click on maps.
To try it, head to http://online.seterra.net/en/ in your browser. You can then choose from dozens of world areas, across all continents. Each exercise is similar - you are asked to click on a particular city, town, mountain etc in the area you've chosen. If you get the right answer, your score increases. After 3 incorrect clicks, the correct answer is highlighted for you to click on.
The game is, to be fair, pretty simple. But if it can help children learn where things are in the world, it can't be all bad. Especially as it's free, too. And there's nothing to install on your computer.
Seterra is supported by advertising. But if you'd rather not see the ads, you can download an ad-free version of the program from the site and run it offline. Personally, I can tolerate the ads if it means I don't need to install the software.