I haven't used Config, and you might get a better response in the iPad in the Enterprise forum - Configurator has been the dominant discussion trend there since it's release. My initial impression, based on what I've read there, is that it would be overkill for managing a few family iPads - you'd spend more time figuring out how to use it than it would take to create one iPad as the "image" and restore every other iPad from the image's back-up. I'm going to be overseeing 6 ipads at work next year, and doubt I'll bother with Configurator for that.
We manage over 6,000 iOS devices for a large school district. Apple Configurator is an easy to use program. It would be very usefull to "supervise" those devices for your grandchildren. You can create configuration files that can prevent them from using the App Store, blocking in-appropriate content, or lock them into an app. I use the App Lock for my 6 month old. I keeps them from accidently clicking the home button and getting out of an app.
Download Apple Configurator
On the first screen under profiles click on the plus + and create a new profile.
Here is a look at a restrictions payload. A profile just a file that contains settings.
Click Apps and then the + button. Import all of the apps your kids will want to use.
Plug in one of the old iPads and select to supervise it
Make sure you put a checkmark next to each app you want to install.
After a long weekend of grandkids drawing, and taking pictures, simply plug the iPads back into configurator and refresh. They are back to their original configuration.
Hope this helps!