The scenario you described would make your UITexture a quarter of the screen size, not half (occupies the top-left quarter).
Anchor the children so that they use the UITexture as the target. For example to anchor some 100x100 sprite to a bottom left corner of the texture, anchor left to left, bottom to bottom, top to bottom, right to left. Right and top would both have offsets of +100. If you want it to be in some relative position on the texture, instead of "Target's Left" etc use "Custom" and specify your own relative 0-1 range position.