I'll address your question, directly, in a moment, but I want to mention 1 thing first. IF, and I say IF you're interested in getting out of the Sale, contact your Homeowner's Insurance Company, perhaps the local Fire Company, and perhaps the local Municipal Office to find out if it's REQUIRED for a Seller to make mention that the home is a rebuild due to a past fire. If he/she/they were required, then you can ask about getting out of the Sale.
Now, assuming you want to keep the house, contact your local Department of Health for guidance. The office may be a Municipal office, a County office, or perhaps a State office. At the same time, speak to your Pediatrician as well. You have LOTS to do.
I do wish you well. My best to ya and hope this helps.
Jay J -Moderator
PS: Even if there was a Doctor on this Forum, I don't think you'd get medical advice via a Forum ...