This was a fun project for my three nephews for Christmas (ages 3, 2 and 2). I thought they'd each like their own little personalized desk for coloring, blocks, snacks, etc.
This was a relatively simple build with the only tricky part being the leg holes (and getting the legs to open at the exact angle I wanted). I had to fudge a couple of them with some patches that you can see in one of the photos.
I would suggest using lock nuts on the bolts. The original nuts I used were turning as the legs opened and closed. I thought that eventually the nuts might work themselves off the bolt.
The frame was built completely out of 1x6 scrap wood I had lying around my garage that had been used for shelves. I cut the 1x6s down to 1x2 and 1x3 with my table saw. I did buy a small sheet of plywood underlayment for the top.