There are many and 3-4 days enough to cover some of below locations Abbey Waterfalls
Coffee Plantation Elephant Camp
River local boating at Barapole River
The Cuvery river source point
You can go to Badami, Pattadakal and Aihole, they can be covered in 2 days and is also easily reachable from Coorg or Chikmangalur. The architecture of these temples have a history and they an architectural marvel. Hope you get to see it.
Guruvayoor temple needs special mention.
it's one of the oldest temples and is literally booming with energy. if you are sensitive to energies then the vibes there are similar to Venkateshwara temple of Tirumala & that of Vaishno Devi.