Comment Re:Gamemaker (Score 1) 237
I used Game Maker a few years ago to create a few games for fun. It is bit of a resource hog but it is easy to use. GM comes in 2 flavors lite (free) and pro ($39.99). The lite version should do everything you want but $40 is not bad for full functionality. GM is drag and drop but it does have a script object. All my game I used the script object for 95% of the functionality. There are very few things that the drag and drops are needed for (bouncing off objects). I hate drag and drop since it does not teach you anything.
The other thing you might want to looking into is finding a freeware or a cheap game that allows for modding. In the early 90's I modded the hell out of Red Alert. The rules.ini file is editable in notepad. Now you can just download Tibedit and have a GUI for modding. I have heard (but not seen for myself) of a mod that turns RA2 into a space game.
I have also recently d/l Aquiria http://www.bit-blot.com/aquaria/ . The website says you can mod and change graphics too. I have been thinking of recreating one of my GM games using the Aquaria engine. Modding is a bit of a side step but it will allow your kids to use an already developed engine and it may give a better foundation for understanding how a good game works before they actually decide to make one themselves.