get some translation cards from Allergy UK, this will help with restaurants and getting medical help if you need it.
We have used them loads of times over the years , very useful.
Are you going self catering? we went to eurocamp so that we could make some meals ourselves.
We ate out a few times and had simple meals.
We have been to Spain, Italy, France with our multiple food allergic son, and daughter was briefly allergic to milk. We have flown to Spain and gone long haul to USA a couple of times.
I would get extra health insurance to cover the holiday, and extra set of meds. For EU holidays we had 2 sets of meds, which contained 2 epi pens, oral steriods, inhaler and antihistamine. For long haul flights and holidays we had 3 sets, one on him, one on me or his dad, and one in suitcase.
have fun, travel is perfectly possible with food allergies!