We found a tester familiar with the gifted via the hoagies list but otherwise we did pretty much the same thing.
We tested in the morning and did not really say too much about it (the psychologist suggested just saying that DS would be "doing some activities").
I think you can only take the WISC or WPPSI once per year, so it is important to get a good night's sleep, have a good breakfast etc. to help give a child the best chance to have a good representative testing session (because you can't go back next week or next month to try again - you have top wait a year OR use a different test).
It might be worth it to see if the tester will calculate a GAI in addition to the FSIQ as relatively lower performance scores which are common in gifted kids could pull the FSIQ down.
