The ornamental design for a toiletseat for children, as shown and described.
FIG. 1 is a front, right, and top perspective view of a toilet seat for children, showing my design.
FIG. 2 is a rear, left, and bottom perspective view thereof.
FIG. 3 is a front elevation view thereof.
FIG. 4 is a rear elevation view thereof.
FIG. 5 is a left side elevation thereof.
FIG. 6 is a right side elevation thereof.
FIG. 7 is a top plan view thereof; and,
FIG. 8 is a bottom plan view thereof.
The broken lines shown in the drawings are included for the purpose of illustrating portions of the toilet seat for children that form no part of the claimed design.