Welcome to the forum!
No, one cannot retake any sections for formal scores. Not within 24 months, anyway. However, sometimes examiners retest for clinical information, such as in situations called "testing of limits". That wouldn't help you for GT qualifying scores, of course, as those are for qualitative information, not quantitative.
I should clarify, though, that you may be under some misapprehensions. Adding 5 scaled scores to a subtest will not raise the composite score by 5 points. That's not how it's calculated. Also, Cancellation is not included in the calculation of FSIQ. It affects only the PSI. So it's actually irrelevant to the presence or absence of a GT qualifying score. Thirdly, you report a GIA and an FSIQ as the same number. There is no GIA on the WPPSI-IV, but there is a GAI, which doesn't include any working memory or processing speed scores, and your reference to something like a GAI suggests that the examiner presented the GAI as the global measure. So a different score for Cancellation would not have affected your DC's outcomes with regard to qualifying scores at all.
On another note, his language reasoning skills on this test are just above average, and suggest that a language-heavy GT school (which many of them are) might not be an optimal fit for him at this time, even though he has strong visual spatial reasoning and fluid reasoning skills.
I agree with Portia that the more important takeaway is that he may need additional intervention for his vision.
