gonna be a pirate or native, he will definitely like to wear clips or chain or scull amulet. Girls are always happy to wear some decorations. But my advice to you- don't give your child expensive jewelry, just give them costume jewelry.

And say them in advance "Please try not to loose this chain (or anything else) but if you loose or break it, don't be upset - it's not very valuable thing. I'm not gonna abuse you". The main thing is to create the holiday in the soul of your child!