Decorate the walls with posters and other removable decorations. Paint the background walls a solid color and use age-neutral picture trim, such as dolphins. Removable decorations make it simpler to change the room when the children grow into their teens. No 13-year-old wants to play in a Barney-decorated room.
Include toys from your childhood, in addition to toys your grandchildren normally play with. Take time to show you grandchildren how to play with the toys and how to take care of them.
Build or buy appropriate storage. Cubbies and toy boxes provide excellent storage options. Teach your grandchildren where each toy goes, and require them to put every toy away after use.
Lay down rugs or carpets, especially if you allow food or water in the room. You shouldn't be too worried about the grandchildren creating messes, so protect your carpet against them by laying down removable protection.
Place a small table in the room. Load up this area with puzzles, books, crayons and paper. Include other furniture, such as chairs and a couch, along the walls of the room for the children to rest.
Include a place to nap if you don't have another place in the house. After the grandchildren have played all afternoon, they'll be tired. If your grandchildren are distracted from naps by toys, the playroom may not be the best option for you.
Phase in toys for older children as they grow up. For example, you can move in a pool table or darts board. Teach the child how to use these items as a way to spend time together and connect.