How old are the kids? That really makes a difference in what they will enjoy.
Some things they might enjoy, with a little structure so they aren't bored and pestering each other:
Jacks, marbles, jump ropes, hula hoops, sidewalk chalk hopscotch
Some kind of art toy like tangrams or a tile set or a felt board; blocks
Handpuppets and a puppet theater
Have theme days -- water play Mondays, cooking Wednesdays, circus Fridays ... (they can "tame" stuffed animals, or have a stick horse rodeo, or make clown paper-bag puppets, or do face-paint, or practice gymnastics and yoga for their circus acts, a different activity every week)