First realize that children's bones look very different on xrays than adult bones do. My nephew (then age 3) broke his pelvis years ago - the othopedist at the hospital sent him home. A few days later they called and had him come back in becuase once the xrays were dry they could see things unique to kids' bones that showed a hairline fracture. (BTW my nephew scooted around on his butt, he wouldn't get up because he knew it didn't feel right. Now as a young adult he's perfectly fine - no permanent issues.)
Make sure the ortho you're going to is board certified pediatric orthopedist. You can find this online when you google his name.
If you're not comfortable follow your gut - ask lots of questions. You're the mom, you're ultimately the one responsible for your son - don't be intimidated. Get a second opinion if you want to - who cares if you feel like you may offend the MD - he won't care - and 5 years from now it won't be a blip on your screen of life.
Bring a small pad of paper - write things down as they come to mind - questions, doctor's instsructions, information, etc. I have found over the years (with my mom's cancer, my husband's spinal injury and my daughters mental health issues) that having a notepad is invaluable. ;o)
Best of luck mama - and have a great vacation!