Dehradun- Mussoorie trip during new years

Hi guys, we're three girls planning a trip form Delhi to dehradun-mussoorie around new years. We want to leave on the night of 27th and be back by 1st of Jan. 1) first of all, is that even a good idea 2) how cold can it get 3) will the traffic be too much 4) what modes of transport will be most optimum 5) and ofcourse, please shoot recommendations THANKS!