Some less generous FT-ers might suggest that if it's so important for the parents, they might want to keep a closer eye on their child during the flight to ensure he doesn't come into contact with a nut.
Very OT: At home in the UK a couple of weeks ago, I read a multi-lingual package of something or other - biscuits, maybe. Out of 12 languages, the ONLY language the 'nut warning' came in was under the English list of ingredients. Made me wonder why it's only British kids who get nut "allergies".