The question of whether to do the T&A in the presence of a sinus infection is a question for the ENT performing the T&A.
The more important question is whether you can do both the T&A and sinus surgeries together, as that would be preferred, as I understand it.
My kiddo had a T&A last spring and is now scheduled for sinus surgery with a new ENT. The new doc is surprised and annoyed that the old ENT did not scan the sinuses before doing the T&A, because it should have been done in one surgery . New doc felt he could tell just by looking at him that he was stuffed. However, he is not infected, just has abnormal tissue in the nose blocking drainage (fix deviated septum, turbinoidectomy, ethmoidectomy). I was surprised that he was surprised that this wasn't handled earlier.