leave the icons where the currently are, in the trash, and wait to see if you see any application with a missing icon.
Chances are that you will not.
There is really no easy way to easily put everything back to where it was, except with Time Machine or by doing an complete reinstall of the system from the Restore CD's that came with the machine. Of course, this would mean that everything that you had done to the Mac would have to be done over again and anything that you created and saved, would be lost.
An Archive and Install, which preserves your data, would also be an option.
However, as I said, leave it all alone until find what is missing.
Meanwhile, do NOT delete the trash.
If you can live with that, your next step is to create an account for your son. One in which he does not have the right to put anything in the trash. Cuts down on the heartburn.
Ok here is what happened when my son was in the FINDER window where it Say's search for he highlighted /selected what looks like many many Images Icon's and other files and moved them to the trash is there a way to just restore everything back and how is this accomplished easily .
Note: The system is brand new I have not set up time machine as of yet .
imac 24 OSX
3.0 Intel 2g ram
Thanks New mac user outdoors101