Writer Storm - A Brainstorming Community

I think your instincts are right and Thriller would be a bit corny. If you've got a cartoony sort of feel going to the story, where there are flashes of gratuitous silliness here and there, then I'd say use it. Or conversely, if the story is dead, dead serious, heavy and angsty in tone and this would shine out by contrast, then I'd say use it - although with that outline I do not think this is the case. If not, then go with your original choice.