How much Angry Birds or Club Penguin can a child take? A lot, but you can probably take less.
If your child is going to be on the computer come hell or high water, perhaps you want to wean him from consuming and onto creating. Your new Macbook Pro, loaded with iMovie and Garageband, may help. For a cheaper solution, you can encourage your child to start a blog. WordPress and other services offer free, simple, anonymous and safe blogging services.