I used JoAnn's brand Sensations Angel Hair Stripes for L. I think that I bought a discontinued color (story of my life)--Turquoise/Cream Stripes, but the Angel Hair yarn is so yummy to work with. If you ever want to try some super soft yarn I would recommend this. It would make a delicious scarf and hat.
For M. I used Moda Dea Ticker Tape color pink passion. Mine is made out of this yarn too--only a camel/tan color.
The pattern I used for the ponchos was Moonlight Mohair Poncho--I adjusted it slightly to fit the sizes of my girls. Only cast on 44 for Miss L. and 38 for Miss M. For myself I had cast on 48 since I am so tall.
This is just straight knitting for about 40+ inches and then fold it in half lengthwise, sewing partially shut and leaving an opening for the head and adding fringe. VERY EASY!! but they are fun to wear.