At the posted coordinates you will find a pouch with an object, that when exposed to UV light, will guide you to the cache. You are looking for the last 3 digits of both the latitude and longitude of the second and final stage of this multi. Please place this object back in the pouch to deactivate it.
Don't have a UV flashlight handy? Don't worry - ambient UV will be enough to give you the answer you seek - (and cause your skin to burn - wear sunscreen kids).
The final cache location will have kits that kids can take to make their own UV detecting bracelets (no need to trade for these items - do trade for any other swag present, though).