Two things here:
The poop fish leave behind will eventually either break down into ammonia or get caught inthe filtration system. In that I include the protein skimmer and any filter you have. If you do have a filter it will capture the poop which will quickly degrade into ammonia and eventually nitrate. Hence the term nitrate factories. Sure, some will still be poop when you clean your filter, but some will have changed.
If you don't have a filter, the poop will liquefy as it goes into the skimmer and form those gross bubbles which become your skimmate. it has been removed from your system.
I only use the filter sock if I have disturbed the sand bed of if a water change has stirred things up too much.
Even tho your son wants to help with the whole process, I would still consider starting before hand. Otherwise he'll have to stare at an empty tank for 4-6 weeks while it cycles, and if he's like my 2 boys, he may not have the patience.
Here's what you may want to do instead. After you get the tank , take pictures of the sand available and some base and live rocks at your LFS
. Let him pick out some rocks for you to buy. Then once you put the rocks, sand and water in the tank take pics of the landscape. I would intentionally make it kinda off. That way you 2 can discuss changes to be made. Hopefully you will be ready for the cuc as soon as he gets home.
During the cycle there is nothing to do. Really you don't even need to do water tests for a couple weeks. A simple nitrate test then and if you have trates test for trites. If/when the trates are high and trites are zero, ammonia should be zero as well ( test to confirm). A pwc
and your done.