I've had a little guy with nut allergies in my care in the past. While I am familiar with food allergies and sensitivities I found it very stressful. I would definitely have the parents sign a waiver and also, if you haven't already, a medical intervention permission form just o cover yourself. When I expected he dcb here I would use Lysol to wipe down surfaces ahead of time. Cetaphil soap for oily skin is also good to have in the bathroom as it removes oils on he skin. The parents used to provide this. You might also post a "nut free zone" sign in your front entrance.