I don't know if I read this right, but as I understand it, you can get Mutable Age at level 6? That seems a little overpowered. Sure there is the pre-exisiting Dragonwrought Kobold Cheese, but this opens the way for every race to do the same thing... You may wish to reword it or restrict the level that players would take this mutation.
As is, you are letting a level 6 character gain +3 to Wis, Int, and Cha. No penalties, no questions asked, and they can do it even if they had started by playing an avarage aged character...