Rowling actually wrote and published a version of "Fantastic Beasts" for us muggles to read. The book is an encyclopedia of creatures, with a foreword from Dumbledore himself. The niffler and bowtruckle are definitely in it.
I love the idea of doing rather than getting. I guess you can choose the ones that you can do- or if you are extra keen do two each day. ~ An Alternative Advent Calendar – 50 Acts of Kindness by kids – Mum in the Mad House