Many say if you need to book online you could if not you could go in person. There is thulabara booking and room booking. For darshan whichever hotel u plan to check in, ask them they will help you.
Udaipur is good to get the glimpse of Palaces, Lakes, Markets, Winter Special Food, Temples, etc all in one place. You can see the Wintage Car Museum, Cable Car Ride at Karni Mata Temple, Boat & Camel rides at Lake Pichola or Fatehsagar Lake, City Palace, Bagore ki Haveli with evening show, Sajjangarh palace on Hill, Neemuch Mata Temple, Morimagri Memorial, Hathipole Market, etc are some of places that you can visit.
If you love trekking then Kedarkantha is the best place for now trek is of moderate level.
If you want to chill in between mountains and take sip of tea in snow then you can go to Auli.
You can check out my timeline if you are going auli or you can send me message if you want to go for Kedarkantha as I'm also going for kedarkantha this friday.