Here is a play table I made using 3 sheets of birch plywood along with some actual plans I put together.
My Son who was 3 years old when I built this was really into matchbox cars, trucks and pretty much anything that he could move around with his hands. A friend of mine got his Son a knock off train table from Toys R Us that was pretty expensive and it was just made out of particle board with one drawer. My Son loved playing with it whenever we visited so I decided to draw up some plans and make him a better one. My wife wanted it to have as much storage as possible. The final product came out pretty good and he seems to love it.
When assembling it, I made sure to use paintable calk around all edges on the top to prevent any spilled liquids from getting everywhere.
Below is a link to an Adobe PDF file I put together showing plans for the table.