DD6 just got her first computer for Christmas, a laptop. Before then, DW and I let her have some highly-supervised time on our machines. And even at 6, her computer is being heavily managed by myself.

At 3, she could very easily, inadvertently click the wrong thing on the computer and render it nonfunctional, so that was our chief concern. Then there are all the ways she could render it nonfunctional from a hardware perspective... dropping, spilling, etc.

There are some simple, cheap learning "computers" at Toys R Us from companies like Leapfrog that DD seemed to like at ages 3-5.