As with all Star Wars films, Episode IX is intense from the get-go and filled with scenes that make your muscles tense up, moments that make you want to watch through your fingers, and reveals that cause you to jump out of your seat. And because the film is so dark — in terms of lighting, though the dark side's influence is ever-present, of course — all of the action tends to feel like it sneaks up on you. If your kids have seen a Star Wars movie and handled it well, all should be fine, but if you have a child who tends to get stressed or anxious when characters are in peril or giant fight scenes are occurring, know that there's more of that in this film than there are calm moments that give you a chance to breathe.
Spoiler alert: some of the most tense scenes are when Kylo Ren and Rey battle (like in the photo above), when Emperor Palpatine, back from the dead, is on the screen, and just the general fighting scenes (of which there are too many to count). A particularly jumpy scene comes right after Rey finds the second Wayfinder.