Hello. You could visit the following places:
Waterfall: Cheeyapara, Attukad
Mattupetty Dam. From there you can visit the indo swiss diary farm & Lockheart Gap
Pothamedhu Viewpoint Top Station for a panoramic view (but it is 50 kms I guess from Munnar so please do check before you go)
Messapulimala is a beautiful trek but it would be great if you hire a guide to show you the trek.
And then obviously the tata tea mueseum
If your budget & time permits do stay a day at orange county it is really beautiful or maybe swing by for a meal at the club mahindra property .
Munnar is very beautiful place in Kerala.you can enjoy many places...Pothamedu View Point (Rajamalai) National Park where also lies the Anamudi Peak the highest peak (2,695 m) of Western Ghats and South India. Tea Museum
Forest Rose Garden,Echo Point, Kundala Dam & Lake, Lakkom Water Falls and Marayoor.