You can go for jim corbett but you wake up early as its around 90 km and can go jungle safari. You go to Sattal as well and can do various water activities as well. Rest it depends on you... Like what kind of hangout place u r looking.
Alka the lake side view hotel or the mannu maharani. You can stay where ever you want.. Both are 4 star hotels as well as situated at best place in Nainital... The view from these hotels are awesome... Gudluck