remember to keep it simple due to attention span being very short.....
what about jingle bells? they could be tied on with ribbon, although i'm not sure how washable they would be, they may have to be removed & replaced ...
you could also make up different games by putting bottle caps under a mesh/see through netting, such as voile so that their fingers could move the pieces on top of the board underneath & not be lost OR use a zipper to add game pieces or-- something simple like a 9 patch [3 in a row]