Why don’t you keep the real world firework names, i.e. Roman Candle, but instead of cartoony monsters aiming/harming/killing each other with fireworks, also change the projectile from ‘fireworks’ to something also cartoony and less real-world? For example, the monsters shoot ‘Star Bursts’ at each other, or ‘Sparkling Dust’, ‘Fire Light’, ‘Cluster Rocket’, ‘Bangers’.
That way you can keep it fun, maintain your intention but it is disguised for a younger audience.
This could also enhance an earlier suggestion of winning spectators.