The ornamental design for a children's activity tabletop, as shown and described.
FIG. 1 is a front elevational view of a children's activity tabletop showing my new design;
FIG. 2 is a rear elevational view thereof;
FIG. 3 is a left side elevational view thereof;
FIG. 4 is a right side elevational view thereof;
FIG. 5 is a top plan view thereof;
FIG. 6 is a bottom plan view thereof;
FIG. 7 is perspective view thereof;
FIG. 8 is a perspective view of the children's activity tabletop shown in an alternate environment of use forming no part of the claimed design; and,
FIG. 9 is a perspective view of the children's activity tabletop shown in a second alternative environment of use forming no part of the claimed design.
The broken lines in FIGS. 8-9 showing two hammer elements and four leg elements, along with the features thereof shown within the broken lines in light grey phantom, depict environmental structure forming no part of the claimed design. The broken lines in FIG. 6, along with all the features shown within the broken lines in light grey phantom, depict portions of the children's activity tabletop that form no part of the claimed design.