You can visit Bhandardara, a beautiful place to spend weekend in Maharashtra. In Bhandardara you can visit Umbrella Fall, Wisdom Dam, Randha Falls, Kalsubai Peak and many more places. If you are planning to come The Yash Resort is the best place to stay. There they have swiming pool and an awesome pool side cafe named YOLO Cafe.
Fir new year if u want a place nearby crowd Mcleodganj is great but if u need isolated places you can go to any places in old himachal like tosh , malana , rasol ,jibhi etc here you can find good secluded places .
You can book a seat in private traveller from chandigarh or delhi as per the iteniary you reaching from mumbai... Then at kasol if you do not have any bookings... you can further ask for the options...
If you have time constraints then visit Lansdowne. If you want to experience blissful nature and great hospitality, visit Almora and stay at HOTs Hostel, Kasar Devi. While in Almora, you could also visit Binsar Wildlife (Leopard) Santuary. If you want to have a feeling of 'Ye India Mein Hi Hai Kya?' go on for Pithoragarh, Munsiyari (simultaneously offering you serene & peaceful time) or visit Chopta/Auli.