What sort of applications will your kids likely use? The Eee PC doesn't come with Windows, and it only comes with a small amount of onboard storage (of which the OS - a customised Linux distribution - takes a substantial chunk). If you do want to install Windows, it can be done, but you'll need an USB CD drive...
The kids are oonly going to use the web (with net nanny etc) home work writing so Word/openoffice or similar along with a spreadsheet program no gaming etc. Would a cheap Laptop be better? I don't mind spending the cash as long as it helps the kids learn.
One point maybe worth bearing in mind, as you say these are to be for learning. An awful lot of "puter litrut" people are, actually, Windows literate at best. Put them in front of anything else and they panic.
Given that your kids will be exposed to any number of Windows machines, the Eee may be a chance for them to get used to the fact that "computer" doesn't always mean "Microsoft". Firefox is a nice browser and OO is fully compatible with any MS formats that may be needed for homework etc.
Even with MS dominating, the ability to use other systems comfortably is no bad thing and best learned before the "computer = windows" mentality sets in too hard. Plus, there may come a time when MS no longer dominates and then anyone who doesn't go to pieces just because the desktop looks different has a natural advantage.