Exploring the Outdoors!
For families who have older children you can take your children out and do scavenger hunts for specific items like pine cones, seeds, leaves from certain trees and so on. Just make sure that each child has a cellphone or that you are doing it in a designated area where an adult is always present. Also make sure each child has basic wilderness training. This means they know what to do if they come across a bear, or know how what poisonous plants and animals look like that are indigenous to the area.
You can also make a game out of catching certain kinds of fish if you were to go fishing. You could also go biking, search for animal tracks or do geocaching. Geocaching takes a little bit more equipment though as you will need a cellphone with internet access in order to take part in any geocaching activities in the area. You may also want to play a sort of eye-spy game where you see how many different kinds of tree species you can identify. Other then this, bird watching and insect catching are popular among all ages.