A Surprise Trip To New York For My Girlfriend…?

I feel like a question blogger…. :)
My girlfriend has never been to New York ( we live in London) and i have found a deal where we can go from 28th December to the 5th January for 1000 pounds ( flights and hotel) – i want to take her as a last minute surprise.
The hotel is pretty basic, but do you think that matters? or would you pay more? i’m just thinking the saved money can be used as spending money.
And although weather is un predictable, does anyone know what weather to expect that time? i haven’t been for a while.
thanks a lot.