T.C.
I think it is okay to help them at that age. Sometimes the task can be very overwhelming to one so little. They have a hard time visualizing it being done, and just see a huge pile of mess. You can make it a game for him. Tell him you are going to set a timer and see how many things he can pick up in 2 minutes. Cheer him on, and make it a game. He's still so little. Sometimes it really helps to limit them to having only one thing out at a time, so therefore, they only have one thing to put away (just the blocks, or just the legos). If they have to clean up a bunch of different things and sort them while doing it, it is too much for their little minds to grasp at once. Be patient. He won't be 3 forever. :)