Given that enough time has passed that a second testing of the WISC shouldn't be artifically inflated by recall of the questions from the last testing, I'd strongly consider re-testing on the WISC. If you didn't have a family history of giftedness, it might be possible that he had just had a good education and was a high achiever. A child with an IQ of 117 is well above average and can certainly perform quite highly.
However, given that it doesn't sound like the first testing situation was ideal and you do have a family hx of giftedness, retesting might come back with totally different #s. I know that I'm not the only one who has had a child tested more than once with rather different scores from one testing to the next.
