Thanks for all the kind thoughts, prayers and good wishes! My son's surgery was a complete success and now he's on the mend. The surgeon had to do a little less than he expected, so only three vertebrae ended up fused instead of 4. Now it's a day or two in hospital, a few weeks with a neck brace and 6 months of healing until he's right as rain.
Thanks again for all your support. Each comment, tweet and email made me feel better.