My boys have been unloading the dishwasher for me for awhile now. I don't think it's ever too early to teach them how to pitch in and help with the responsibilities of running a smooth, orderly and clean household. In fact they dig doing it, begging me to help. I encourage this desire they have and let them help me whenever they want (unless I'm in a hurry and just need to get it done, in which case they are content to just observe)!
Believe it or not the only dishes that have been broken are not due to them putting them away, rather when they clear off their dishes from the dinner table. One or two have been dropped in the sink a little too rough therefore cracking them to pieces. How can you scold them for that? So I don't.
Here's Isaac putting away the bottom half of the dishwasher, you can just see the pure joy in knowing that he's being helpful, he makes me smile!