Shockley
Maester
Good points. I think starting with the ominous part of the scene would be a nice hook, though it comes at the cost of the lighthearted stuff I'd also like to keep in there before the darker stuff sets in. I also want to keep the part where Vincent and Ariel explicitly mention the danger, since it establishes that they've known it for a while ("We have this talk every year." "Yes, and you know why." etc.) and makes sure the reader knows something's up as well.
Well here's the issue I have with that: Your story from what little I can tell is fairly dark (starting with a kidnapping at all), so you have to be really concerned about tone. It's alright to be light-hearted, but I wouldn't suggest starting out like that.
Harry Potter is a great example. The first book starts with something incredibly dark (the death of Harry's parents and his life with the Dursleys) and ends with something dark (the revelation that Voldemort isn't as dead as they think, oh and hey there's the dead body of my teacher.). It ends in the same way it starts - dark, foreboding of things to come.
No scene is fully light-hearted throughout the series. Plenty start that way, but they never end like that - it could be the happiest Christmas ever, but you can bet your life that some awful/foreboding/evil gift will be delivered by the of the night. If they're enjoying some new wizarding experience that is cute and magical, you can bet Malfoy is going to show up and rain on their parade. Etc.
So the light-hearted can't be there for the sake of light-heartedness; it has to fold into the darkness and, as written, that doesn't happen in your first chapter.