Hi n19,
Used to live in Spain and our DS has nut, seed and egg allergies.
Definitely make sure you take your Epipen with you plus even pack some Piriton (can buy over the counter in local pharmacy before you go) as a back up and carry both with you.
The translation cards from allerywise should give you the sentences to speak / or point to in a restaurant plus if you do need to go to a hospital, then keep the card with you all the time.
Ice cream wise on the beach, for example, we found normal Callipos were fine and were not made in a factory with nuts.
The other thing to say is to look for the phrase 'frutos secos (nuts in Spanish)' and if this is anywhere on packaging, then we steered clear.
If you're really worried and also going self-catering, maybe stick to brands that you know or even shop in English / British supermarkets.
Not sure if that helps - good luck.
Helen