I just read the Wings of Fire books and, trust me, you’re not too old for them! They’re very well written and pretty dang brutal. o_o The gravity of the situation is pretty well addressed in all of the books thus far. I couldn’t read past the first Ga’Hoole book for the same reasons you mentioned, but these books do a much better job balancing out lighthearted stuff with action and drama. All the different dragon cultures were rad, too.