I’ve heard about catching up w/o using a kosher megillah as well, but that it was for minor misses (like a word or two) not paragraphs.
My oldest is very good. He can sit quietly if you tell him to. He regularly goes to shul with my husband and behaves. I brought him to megillah even as a young baby/child without issues.
Unfortunately, the women’s section in my shul is so noisy with kids, that while you can hear, I’m not sure what to do with my 17 month old. Bring him? Not Bring him? We’ll see what happens.