Kriston,
Did you say whether or not your son enjoyed taking the test and liked the tester? Once my son took his first individual test, he couldn't stop talking about how much fun it was and how much he wanted to do it again. Since we wanted to get more info anyway, we did the second test. But if he hadn't wanted to do it, I doubt we would have. I think that the WISC would be very unlikely to be successful unless he was on board with it.

It sounds like you have some time to decide. Since he's only 6, you could wait a year and still be well within the ceiling of the test.