Measure yourself across the bust from under your arm to under your other and halve this measurement (A). Measure the height you want going over your bust (B).
Trace the kid's piece and trace it onto a large sheet of paper or a paper bag.
Measure side to side and subtract that from (A). Whatever's left, add it to the center of the piece, plus seam allowance to the outside edge only. Just draw a new line that many inches over. This is the side that will be on the fold, so when cut out, will be twice as wide.
Now measure it top to bottom and ubtract that from (B). Take what remains of (B) and add half to the top and the other half to the bottom, plus seam alowance for both top and bottom.
Take that piece and cut on the fold. Gather it alone the bottom to fit over your bust neatly instead of hanging off your boobs.
For the skirt, cut several inches longer than stated since you're taller. For width, measure around your bust and add, say, 6" to their measurements for a not-too-gathered skirt, on up to however wide you want to.