You are rocking this.
I would go through the process with the attorney. If the school still fails, then maybe file with OCR, but go through this process first.
In the meantime, I would find out how your OCR has ruled in food allergy cases. I will tell you that regional offices some are notoriously better than others. For instance, when we were looking to move a couple of years ago, DH was contacted by an org in Missouri for an interview. I said NO WAY--based on several members' experiences with schools and FAs in that state--and two members' dealings with that OCR.
Living in Virginia, I had a pretty high confidence in that OCR, based on their rulings and in one of my two conversations (the other one not so much).
I think it's good to have a. Idea of the lay of the land with your OCR. Not that if you were in Missouri (or a place where they had not made rulings in favor of the FA complainant) you would avoid filing a complaint. but to know what you've got.