Any child would get a kick out of pulling up a chair to a one-of-a-kind game table like this one, particularly if he's had a hand in creating it. Applying the self-leveling polymer finish is definitely a job for adults only -- but the good news is that it pours on and, once cured, it's waterproof.
First, have your child experiment with different tabletop designs by arranging the collected items on a similar size surface. Once he's settled on one he likes, mix a solution of 3 parts glue to 1 part water.
Working from the center, brush some of the glue solution onto a small section of the tabletop, then help your child transfer the decorative objects to the glued portion.
Use your fingertips to gently press air bubbles out from under each object. Continue decorating the table, a section at a time, until the whole surface is covered.
Once the glue is completely dry, you can apply the clear, varnishlike polymer finish. Carefully follow the manufacturer's directions, which may vary from product to product.