Just came back from our vacation and the games you suggested were a real success. The only problem was that my kid and his friend preferred taking turns at playing with my iPod rather than playing with their Nintendos. I think part of the attraction is that the controls are so simple that they can figure out how to play very quickly and that the prices for the games are so low which means you can buy a lot of different games on your iPod for the same amount of money you'd have to pay for one single Nintendo game. Guess what he wants for Christmas ...
As soon as it's out, I'll head to the App Store. As for Real Racing being too difficult. I bought it today because it was on sale. It took him 5 minutes to figure it out and then he ended a race in 3rd place. Right now he's having lots of fun with it.
Spider, enviro bear(it's the best worst game ever!), and imech... Edit: hybrid when it comes out. I'm one of the testers an it is awesome.