We recently purchased the "Classmate PC" for our DS(almost 5). We chose this one vs. others because we felt like it offered the best design value for the price. It is rugged/durable, features the ability to be a tablet and a touch screen. It does come with some software for kids and a special "front screen" that can limit their access to internet, etc. if desired.
Like all "netbooks" it does not possess as much memory, etc. as a laptop would.
I'm sure the website can do a better job explaining it than I can but feel free to ask if there is anything I can answer.
http://www.classmatepc.com/
