Having trinkets opens the posibility of getting your heroes in situations where they have to prove themselves without their powers and/or justify why they can`t just get out when they get captured. Also, making it a trinket makes powers easier to transfer (specially if the powers are inherited through generations)
It can also justify boosts in power and can be a motivation for some adventures (like in digimon when the chosen kids had to look for the 8 emblems to achieve a stronger digievolution and to put a fight against stronger enemies)
Making their power activate through sheer force of will can work too. You can even explore how the emotions of your heroes affect said powers and their activation. For example anger may make Flare`s flames stronger but harder to control.
Also, you can make a combination of both, maybe the trinkets are activated by their emotions/willpower
See what works better for your story.