The pixie cut is very popular with tweeners so the answer is yes!!
This age is an ideal time to experiment on styles to get used to finding out what suits their face shape and personality etc. It also helps avoid making a drastic hair style change when older (we all know how that can go!) and its fun ...More >
In Reference to Miley Cyrus ... her particular style is VERY short on her temples and nape so I would suggest some thing a bit longer, still shaped over ears and nape , but not necessarily buzz cut(as hers is ) You didnít say if your girls hair was straight, curly , thick , fine ? all of the mentioned can have a pixie cut tailored to hair type . Re the long Side fringe(bangs) the fringe should be a graduated cut chipped into. A good guide for length is for the start to be on eyebrow and the end just long enough to hook over ear ..
The shorter fringe should be layered and although still asymmetric not so steep.. I suggest you look on the hairstyle finder tab on this site ..there are lots of variations and you can have a bit of this, and a bit of that, makes it more individual for your girls.
They can play around with products too and clips sleeking it back, funking it up and pinning the sides to mention a few options .
Hope they love their new haircuts ....