Are you looking for a simple summer time activity? Why not a homemade tangram? They are relatively easy to make and take strategy to solve.
This one is of a rectangle. I just drew the rectangle and split it into other shapes by drawing lines from place to place. Then, I cut out the shapes and taped them on a piece of paper so I could scan it onto my computer and upload it here. (You wouldn't need to do the last couple of steps if you are doing for someone at home to solve.)
For older children, maybe make a game of it. Show them how to create tangrams and have them create one for each other. That way, they can see who solves the tangram first. Or, have them create one for you, so you both can be working on tangrams together. It is a nice way to spend some quality time with your children. It is also an activity that can help the child (or adult) keep their brain active.
Activities like this have been shown to curb the onset of things like dementia and Alzheimer's disease. So, it is a wonderful idea to get children interested in keeping their brains active early in life and keep doing brain activities like this into adulthood. Work on them together as a family. You will all be better off because of it. Do what you can to make it exciting!
Feel free to print this tangram out and try it! Let me know if you want the solution! But... then, try your own! Keep exercising your brain!