Four years old? Try to find copies of the Putt-Putt series (Putt-Putt Saves the Zoo, Putt-Putt Travels Through Time, Putt-Putt Goes to the Moon), the Freddi Fish series (Freddi Fish and the Haunted Schoolhouse, Freddi Fish and the Case of the Missing Conch Shell, Freddi Fish and the Monster of <Something> Cove), or the Pajama Sam series (Pajama Sam in No Need to Hide When It's Dark Outside, Pajama Sam in You Are What You Eat From Your Head to Your Feet, Pajama Sam in Thunder and Lightning Aren't So Frightening).
These are all kid-level adventure games with a point-and-click interface. Originally developed and published by humongous Entertainment, I believe Hasbro Interactive may be handling them now. The re-releases have slightly different names, but the games should be the same. Look on Amazon (a quick search of Pajama Sam brought up all three titles for $6-12 each) or eb@y.
Also by the same developers are the Backyard Sports series. I haven't actually played these myself, but they are supposed to be decent sports titles for kids.
Casual games (like those from Reflexive or Popcap) may be a good idea as well.
Hope this helps. PM me if you need more recommendations - I would have to check my list at home to see what other titles I could suggest.