Idr what books it was cus read them in elementary school but I remember there’s a timer on their power where if they stay as an animal too long they get stuck. I remember this cus at one point they make a long trip so they have to shift back every few hours but get stuck half way.

Also some evil character turned into a bird or falcon or something and forcibly turned a couple characters into flys or something and yeah

These were books that are good to be in an elementary school