I dont think you can any place in North India with 'huge massive fireworks'. As far as I know, Shimla is your best bet as theres a lovely church there. Manali is also known for its celebrations. Delhi can also be considered, although there wont be any fireworks as far as I know.
Sorry, m not Christian as I believe to lord shiv. I just wanted to know places where I can see nice decorated Christmas tree and firework count down party at India.