Hi Amelie
I haven't done the trip to New York, but I have done several JY holidays. What I can tell you is that it definitely won't feel odd. Everyone with you will also be going alone, but you will be together. Everyone has their own reasons for travelling alone, and as you get to know each other, generally a few stories unfold, especially after a few glasses of wine. Some are divorced, some bereaved, some single from choice, some have partners who either don't enjoy traveling or who are unable to travel. This sort of group makes for a great distraction from what, for some, is a difficult time. All will be hoping to meet new friends and share experiences with them.
I hope you have a great time - I'm sure you will.
Toni