My daughter had Hip flexors, abductors and hamstrings done in September.  She turned 12 in April.  She scissor walked and on her toes.  The doctor was not sure how well she would do, and was somewhat apprehensive partly do to how mobil she was.  She uses a walker or crutches.  She has great success and was real motivated to get up and moving.  In fact tonight she stood and took 3 steps gave me a hug and kiss (I need them after a long bad day).  A few things to consider when they are small they still have a lot of growing to do might have to have the surgery again at a later date.  My daughter had gotten so tight she could barely take steps and tired very easily.  I figured she had nothing to loose.  

Have you tried leg immobilizers and or a bar to sleep in?  we do that when she was you and less tight.  In January she was able to do 20 laps around the gym every day and out of all bracing.