My Son Has a Novelty Kid Item He Wants to Start Selling.

Depending on what his product is, you need to make sure there are no patents or trademarks on it. Depending on what it is, you might need a patent so you need an attorney to help you with that process.

That said, you could go the route of Etsy to try to sell. My daughter has some favorite stores on Etsy with unique products she buys from routinely.

Without knowing what type of product you are talking about, it is hard to answer the question. Does it need a prototype, market test, how is it produced?

My company is in raw materials, plastic, and I am often contracting with labs to specify a formula for a product that can withstand the sun, degrade in a specific time, hold up to drop tests, etc.

There is just so much info we have no clue to and so many different avenues he can take with his project.

You can get cheap advertising through PTA programs that sell football and athletic programs at games, flyers, etc. You DO have to pay to advertise, not just solicit vaguely.

Good luck

Etsy is the best site for independent crafters. Of course as his parent you should set up and monitor his page.

Why limit his market to 'mother' geared sites?

In order to sell anything here he's going to have to go through the process to become an official vendor.

CraigsList, eBay, Amazon, and Etsy he can sell online.
Yard sales, craft fairs, local farmers markets he can set up a booth (he'll have to pay for table space) he can sell there.
He might need to get a permit - check your local laws - in some areas even a roadside lemonade stand can get into trouble if they don't have a permit.

if you want to advertise? Then PAY to advertise on this site and others.
If he made it himself, maybe he needs to get it patented? Or apply for Shark Tank and get their help