Being prepared with a safe treat box has helped my daughter, as has preparing for not being able to take part in every snack or treat at school, family parties, play-dates, sleepovers, and social gatherings.
For ideas on how to include all of the children during class celebrations, check out my food free treats and craft ideas on Pinterest https://www.pinterest.com/ThriveWAllergy/non-food-birthdayholiday-treats-for-school/
Also take a look at the books, and information for Elementary teachers that I have collected here:
http://thrivingwithallergies.blogspot.com/p/resourses-to-share-with-c.html
Being prepared goes a long way!