It's always good to set your expectations low. Although Simon did freak out about taking his shoes off and didn't want to stand on the scale, he did not have an epic meltdown. Instead, he just did his monkey cling and protested, but there were no tears. So we did the "weigh mom and child then just mom" approach (math) to derive that Simon weighs 25 pounds.
For the rest of the time he did OK. He didn't cry when they pricked him and squeezed blood out of his finger. And he didn't cry during any other parts of the exam, probably because the kind doctor let him sit on my lap the whole time.
Actually, he cried most when handing him over to his teacher when I dropped him off at daycare after the morning appointment.
As far as his stats, he continues to be on the small side, but we consider him normal-sized and just assume all the other kids are too big.