Hi Avishek, Sure, here is a 5N/6D Meghalaya itinerary for you: Day 1: Arrive in Guwahati, the gateway to Meghalaya.
Check into your hotel and relax for a while.
In the evening, go for a walk around the city and explore the local markets. Day 2: Take a scenic drive to Cherrapunji, also known as the "Wettest Place on Earth".
Visit the Nohkalikai Falls, the tallest plunge waterfall in India.
Hike to the Seven Sister Falls, a series of cascading waterfalls. Day 3: Visit the Mawsynram village, which is even wetter than Cherrapunji.
Go for a walk in the Mawsynram Market and buy some souvenirs.
Visit the Living Root Bridges, a natural wonder of Meghalaya. Day 4: Drive to Wari Chora, an offbeat village in Meghalaya.
Hike to the Wari Chora Peak and enjoy the panoramic views of the surrounding hills.
Visit the Wari Chora Caves, a sacred site for the Khasi people. Day 5: Drive to Dawki, a village on the border of India and Bangladesh.
Visit the Umngot River, a crystal-clear river that is popular for river rafting.
Go for a swim in the river or just relax on the banks and enjoy the scenery.
Day 6: Drive back to Guwahati and catch your flight back home. Here are some other offbeat places that you might want to visit: Mawlynnong, the cleanest village in Asia.
Nongriat, a village with hanging bridges.
Jowai, a hill station with beautiful scenery.
Balpakram National Park, a biodiversity hotspot. I hope this helps!
That's a nice destination but you have very little time, considering you want to do adventure stuff as well as visit offbeat areas. Meghalaya has good roads but it takes time to travel between places. My advice would be to keep one day dedicated to any one adventure activity and keep the rest of the time to enjoy the beauty of Meghalaya.