Popped Bubble Art: I've done this activity with my kids a few times now and it never fails to fascinate them - and me! Simply color bubble mix with food coloring and blow bubbles onto paper - as the bubbles land and pop, they create beautiful works of art. It goes without saying that this project is best done outdoors. A great one for those lazy summer afternoons.
Build your kids their very own tire seesaw! http://diyprojects.ideas2live4.com/2016/03/01/build-a-seesaw-from-repurposed-tire/ This DIY project is a very great alternative to the usual, metal seesaws you can buy. A tire teeter totter is light and movable so that you can easily relocate it if you need to! It can also be customised to suit your child's personality. What's not to love? Do you know anyone who would love this idea, too? :)
Summer Party Game - Shaving Cream Balloon Tag - Attach the balloons to everyone's waist with a safety pin. Kind of like flag football, but the object of the game is to pop everyone's balloon. One person is "it" and everyone whose balloon gets popped is then also "it." It's definitely an outdoor game and it is a blast!