I think you have to choose your date at 1st December 25th or 26 ,27 or 28 th Dec you must be stay over there as December 31st night at . because in that time lake city Udaipur will looks like really queen & anjan . I can't explain that how it is but after that you can go for jaisalmer. I will suggest that you masti take a bus from Udaipur to jaisalmer. because , when you enter jaisalmer, that will be a free morning time. if your luck is good then you can see from your bus window when bus is running , minimum 50 to 60 Deer running with your bus. what do you like to say about that. so keep enjoying and take care yourself.