Whenever I buy a new system I like to stop at the used stores (like EB games or Gamestop) or ebay and pick up a few games that I may have missed out on.
Here are my suggestions
Find the used 2 pack game Forza 2 and Marvel Ultimate Alliance. I picked it up for $10 a few months ago. Forza is a good driving sim, and me and my 5 year old play Ultimate Alliance all the time.
Other games my 5 year old loves are all the Lego games like Lego Batman and Lego Star Wars Complete Saga. You can probably find the used 2 pack of Lego Indiana Jones and Kung Fu Panda which are 2 other games he likes as well on the cheap now as well.
Other decent older driving games that your wife may enjoy are Dirt and Sega Rally.
For you I highly recommend picking up Bioshock it may be classified as a shooter but is really story driven. Also try out Gears Of War (part 1) I did not like shooters at all until I bought this game it really is amazing. Also give Mass Effect a try.
