Converting long-sleeve shirts into short-sleeve shirts

My son is growing so quickly that it's hard to keep up! I find myself constantly going through his clothes and picking out things he's too tall for, or shirts that are too short. Sometimes, though, I come across shirts that still fit great, but are long-sleeve. I know that I've got 2 options—throw in the donate pile, or convert them into short-sleeve shirts. They definitely won't fit him by winter.

Being a thrifty mom, I decided to convert them. Here's how I did it (if you don't have a sewing machine, look into hemming tape, which you can find in any fabric store):