Hmm, interesting one (I'm a huge HP fan).
I am the same age as the Harry Potter actors, it was cast when I was their age so I would have been about 15 or 16 when I watched it.
I think the Prisoner of Azkaban is pretty creepy in itself, if they've seen that one.
The Goblet of Fire has a bit of a dark storyline throughout, and it loses the comedy elements of other films such as the early ones and the one with Umbridge and the twins. I'd say it's the darkest, because it doesn't have the humour of some of the others (because the book is so big they tend to cut the humourous stuff out).
It starts with Harry seeing an old man being murdered by nagini the snake. He then goes to the Quidditch match wheere the Death Eaters descend and set everything on fire. Moody joins the school - a creepy man with a magical eye. The Triwizard Tournament starts with pupils from other schools. Harry gets in even though he's underage so no one can understand how he managed to break it. The task with the dragon is pretty harmless but the one where he has to rescue people from the water is quite grim. There's a creepy bit with Barty Crouch who is behaving very oddly. Cedric is killed by Voldemort after transforming from being a creepy baby. There's a bit at a graveyard where he speaks to the death eaters and then Harry brings Cedric's dead body back. There's then a bit where it's revealed Moody is actually Barty Crouch JR and the real Moody is hidden in a trunk - and it was him who put Harry's name in the Goblet to try and kill him. the Dementors then murder Crouch.
So all in all - I'm not sure. It depends what your kids are expecting from it. 1 and 2 are quite jolly and funny in between the creepy bits, this one isn't, as it is the turning point for the series getting darker.
In terms of the overall arch, they wouldn't miss much from not seeing this one, it kind of stands alone in terms of the story.
I would suggest watching it yourself first, and watching it with them. You know your kids better than we do.