The pattern is the free Sunny Day Shorts from Oliver & S. I highly recommend the pattern. You can download a huge size range in two pdfs, one from 6 months to 4, the other from 5 to 12. I figure I've got the kid's shorts needs covered until he enters high school. It's a very straightforward pattern. If you're after pockets or ruffles or other bells and whistles, you'd be on your own. But this is a nice blank slate; you could do a lot of fun things with it. Plus: free!
I was lucky enough to find a packet of 6 cactus patches at a local gardening store. I plan to trickle them into his wardrobe one by one.
The Man has suggested that the kid may not like cacti. It's hard to know until he starts talking. Until then, it'll be all cactus, all the time!
My pattern review is on PatternReview.com here.