Instructions
Find a game idea. It doesn't need to be original. You can build on an old favorite such as Pin the Tail on the Donkey or a tossing game. Or, it could be something you devise, a building game or a guessing game.
Make the rules. Keep them as simple and fair as possible. Make sure they don't require skills beyond the children's capabilities. You can adapt the rules of familiar games (horse shoes become ring toss or pin the tail on the donkey becomes pin the crown on the princess) or use a board game as model for a more active game (the kids can only walk the number of steps determined by a dice roll.)
Use items from around the house. Buckets or gardening stakes make good targets. The kids could toss Nerf or ping pong balls, plastic hoops or rings.) Draw a donkey on butcher block paper, and let the kids make tails from construction paper. If you can't improvise at home, make a quick trip to the dollar store for cheap supplies.
Prepare to mediate. Kids can sulk, become aggressive, tease each other. The quicker you step in to soothe over feelings, the more fun the game will be.
Give out rewards. You can give small rewards for winning game stages, slightly bigger rewards for winning the game. You don't have to spend a lot of money, trinkets from the dollar store will do nicely.