The ornamental design for a cover for playyards and cribs, as shown and described.
FIG. 1 is a top, front, right side perspective view showing our new design for a cover for play yards and cribs.
FIG. 2 is a bottom, front, right side perspective view thereof.
FIG. 3 is front view thereof, the back thereof being a mirror image without claimed subject matter.
FIG. 4 is a right side view thereof, the left side thereof being a mirror image.
FIG. 5 is a top view thereof; and,
FIG. 6 is a bottom view thereof.
The broken lines adjacent the shaded areas represent the boundaries of the claimed design, while the other broken lines depict environmental subject matter only, and form no part of the claimed design.