I’d have to agree with the Gamecube. It’s a dead system, but as everyone has said, the machine is cheap, and the games are cheap, and it’s absolutely loaded with kids games.
The controller is also very kid friendly. For the most part, everything is controlled using the BIG GREEN BUTTON. And it is probably a good size for a kids hands. I have both the normal “duke” controller, and the smaller “S” controller for my xbox, and my wife actually cannot comfortably use the controllers, as her hands are very small. She can use the GC and PS2 controllers comfortably enough though.
Also, for the most part, the games are accessible. There are certain ones that are not really for kids (Resident Evil, Metal Gear etc) but even fighting games like Smash Bros. are kid friendly… big cute characters, no blood. The kid friendly motif is spread nicely across the whole range, mostly from first party Nintendo product (kart racing, soccer, tennis, golf, previously mentioned Mario Party).
And don’t forget it also has exclusivity on Pokemon.
At age 10, you’ll get a good couple years of play out of it for the oldest child before it really becomes too uncool for him to play it, and by that time the new Wii will have come down from it’s already deliciously low price, and when the older kid moves on to the next generation, the Wii will still play all your old GC games for the younger ones, using the controllers they’re used to even.
Even my mother was able to get into a gamecube. She has her own. For myself, I only packed my GC up last week so I could make room for the Wii that comes out here in December.
On previewing that post, it seems as though I really were a Nintendo fanboy. I assure you that I do like Nintendo, but my reasoning comes from owning all of the currently available consoles, and selling them for several years.
The points about software availability are good ones though, but if you’re OK with using Ebay, it will never be a problem. And historically, stores like EBgames have sold pre-owned copies of older systems for quite a while after the new ones are gone. They might be kept out the back though, and not taking up shelf space. In the back rooms of many stores around now you can still find dozens of Nintendo64 games, and that machine has been dead for 5 years.