Indoor or out kids of all ages love obsticle courses.
Building them is half the fun! Use a variety of cardboard boxes, blocks, lawn chairs, balls and pillows. Consider blankets, tunnels, ottomans and tunnels. Every time you make it, it can be different.
Safety of the younger children is of special concern.
Use soft or "nerf" balls, and be considerate of furniture edges or any other hazards.
How can I make an easy costume?