Get him the DS. He will love it, you can easily limit time on it and it's a great bargining tool eg: do your homework, tidy your room etc and then you can have 20 mins on it.
DS1 is 8 and he got one at 6, got him one game, we rent others from the library, he loves Brain Training too.
I would still well clear of the Magnetix, the same DS swallowed one of the balls when he was six, hospital x-ray etc, no pain or harm done, but I had to ensure it had passed, so I had mash his poo everytime to try and fine it , rubber glove inside 2 bin bags, hand down loo, gagging.
I did this each time for over 10 days, then he 4got and flushed, but there, as is by magic, was the Magnetix in the bottom of the toilet bowel. It was no longer shiny due to the stomach acid, he took it in to show and tell at school, sort of a moral tale/science project if you like!