Do you have any maps lying around your house for your kids to explore? We get them for free from time to time and keep them to use for crafts. Open up a map and just talk to your kids about north, south, east and west. Show them the different names of the ocean. Talk about how much of the world is covered by water. Talk about what it means to be a continent compared to a country or a state or city. These spatial distinctions are important first steps to understanding geography.
If you need to find a map, an amazing resource to view really old maps online is http://www.oldmapsonline.org/ [Thanks Library as Incubator @IArtLibraries for sharing this information]. This British government site can show you many parts of the world and how our understanding of shorelines and boundaries changed over the years as people explored territory and created more sophisticated mapping techniques.
Activity: Creating a treasure map is a sophisticated way to play hide and seek. After exploring some maps, have each child hide an object in the house. Then ask them to draw a map for you to find it. Or you can draw a treasure map that leads to another map with more clues. There are many scenarios to pick based on the age of your kids.
Books: Treasure Island by Robert Louis Stevenson and illustrated by Robert Ingpen. For a picture book version of treasure hunting try I Spy Treasure Hunt: A Book of Picture Riddles by Jean Marzollo. Choose any of the I Spy book series for a treasure hunt in a book.