I found this tutorial online and loved the idea: http://thismamamakesstuff.com/tutorial-slim-slack-for-boys/
So I went to Goodwill and found two pairs of pants for about $6 total. The first pair I got are a very lightweight corduroy with pineapples embroidered on them:
Here's the result! The only thing different on this pair of pants, is that instead of sewing the elastic in the back waistband in each side seam, I sewed it in one side seam,and put a buttonhole in the waistband near the other side seam, and used that elastic that has buttonholes in it, so it makes the pants adjustable. (did that make sense?)
The second pair is a brown and white stripe. I was looking for seersucker but this was the closest I got:
This time I widened the legs so they are more straight leg:
I love that I get unique pants for just a few dollars!!