Hi Diane, I've flown frequently since getting my ostomy. I find that with the body scanners my ostomy always shows up, so I've developed a very easy method that has worked countless times. I just verbally (quietly) let the TSA agent who is immediately next to the scanner know I have an ostomy and where I have my medical supplies ("Hi sir, I have an ostomy that's going to show up on your scanner. Also, my medical supplies are located in that blue bag over there.").
Experienced agents just have me touch my clothes over the bag with my hands and then test my fingers for bomb residue, as well as testing any liquids I carry over 3 oz (wound cleaner) if I'm carrying them. Only once I got a light patdown, but it turned out it was the agent's first day and she didn't know what to do. The whole thing takes an extra 90 seconds to 2 minutes usually, and everyone is really nice about it. It makes me wish I could bring a camera along to show people that it's not nearly as bad as you might think (I wish I knew before I flew that first time, since I was so nervous!).
Hope that helps you and your son!