The ornamental design for a playhouse with tentextension, as shown and described.
FIG. 1 is a perspective view of a playhouse with tent extension in accordance with our design.
FIG. 2 is a right side view, it being understood that the left side view is a mirror image thereof.
FIG. 3 is a front view thereof; and,
FIG. 4 is a top view thereof.
It will be understood that the broken lines throughout the various views are included for purposes of illustrating portions of the article which form no part of the claimed design.