I STRONGLY recommend testers on the Hoagie's list, who are familiar with testing gifted children. If they plan to give the WISC, I would also ask if they typically utilize extended norms when they are needed (Hoagies list testers are probably quite familiar with these), and when they would calculate a GAI (can be very helpful with a gifted child, who often might have lower index scores).
I agree that it is probably helpful to have ability and achievement scores for advocacy. Also, I would probably focus on and request tests the school is likely to be familiar with (those used for their G&T or accelerated class selection, for instance).
Best wishes!
