The CogAT publisher website has samples of item types:

http://www.hmhco.com/hmh-assessments/ability/cogat-7#overview-content2

CogAT is normed by age, so he should be taking the test for his current placement. Note that he is likely to be taking the picture format (first column), as he will be an entering 2nd grader at the time.

This page of the link you posted notes that ITBS will be one grade level above his current grade placement:

http://www.lwsd.org/Parents/Accelerated-Programs/Quest/Pages/1-4-Student-Selection.aspx

If he is already on an IEP, and has small group testing as an accommodation, I would contact the district GT coordinator (you may wish to cc his special education liaison/case coordinator) and make sure that he has access to his IEP-mandated accommodations for the CogAT and ITBS assessments. (The Renzulli is a teacher rating scale, so accommodations are irrelevant.)

...pronounced like the long vowel and first letter of the alphabet...