If you have 4 full days in Yangshuo, you are going to be able to see most of what Yangshuo has to offer and let Sam put them together for a better and feasible visit when you are in Yangshuo.
For sightseeing lovers: Day 1, Li River Cruise in the morning, Shangri-la Park in the afternoon, Impression Sanjie Liu Show (Light Show) at night.
Day 2, Bamboo Rafting on Yulong River in the morning, Water Cave and Moon Hill Park in the afternoon, Cormorant Fishing Show at night.
Day 3, Longji Rice Terraces, and stay there overnight.
Day 4, Sunrise at Longji Rice Terraces, and then to the airport or train station in Guilin. (Day 3 and Day 4 can be moved up to Day 1 and Day 2)
For Photographers: Day 1, Early morning visit to take pictures of Husband Mountain Sunrise, and then go to Yulong River for sunset.
Day 2, Early morning photo session in Xingping with the cormorant birds and fisherman, visit Yangshuo TV Tower for sunset.
Day 3, Green Lost Peak for sunrise early in the morning and then leave Yangshuo for Longji Rice Terraces and stay there overnight.
Day 4, Longji Rice Terraces's Sunrise, and then to the airport or train station in Guilin. (Day 3 and Day 4 can be moved up to Day 1 and Day 2)
For outdoor lovers: Day 1, Biking in the morning, and Rock Climbing in the afternoon.
Day 2, Hiking.
Day 3, Scooter Riding.
Day 4, Biking in the morning, and Rock Climbing in the afternoon. (You can also sign up for a 4-day Rock Climbing Training)