I have been at both farms. The Hygeia farm is a real farm, which happens to be open to visitors. You can see how they grow their products, pick your own vegetables, and even adopt a goat, but it is not a place oriented at visitors. In the area of Hygeia, there are a lot of restaurants if you want to make a day trip out of it. The Sunyuki location I visited is one of several of their sites. Two Sunyuki sites are ready for receiving visitors, the one I visited (near Qingchen shan) and one closer to the highway to Dujiangyan. The two sites open to visitors have products growing (and some animals) but they do not focus on quantity but rather on the ‘outdoor’ experience: see how things grow, be outdoors, etc. They also have several large farm sites around Chengdu where they grow most of the produce, which may possibly also be visited but are not equipped for visitors (as in providing lunch and activities).Their website shows the general locations of those sites.
On this map https://www.google.com/maps/d/edit?mid=znAMkI9YZP60.kiHB6ykXsvUo&msa=0 you can find their locations, and also the location of a place called Xinjin Idyllic organic farm, which I have not visited myself.
On this page https://groups.yahoo.com/neo/groups/chengdukidsoutdoors/files/Destinations/ you can find information about all three of them.
Have fun exploring!