Hi, 

Great question and project! 

It may be beneficial to do a little bit of both of the projects that the professionals are recommending. The uphill conservation landscaping will slow the water coming through the property so it doesn't have as much velocity, but you will likely still get some standing water in a heavy rain event. 

If the company installing the rain garden is strategic and careful, the roots should be ok. As long as they don't remove more than about 1/3 of the root mass, the trees should be able to rebound. It would be beneficial to consult with an arborist to get their opinion on the trees and potentially cutting into the roots. They will be able to assess the health of the trees and determine if they are healthy enough to leave (we can't determine their health due to the time of year from these photos). You can search for a consulting arborist at https://www.treesaregood.org/findanarborist .

Let us know if you have further questions. 

Emily

You're welcome! If you are open to sharing photos of the process, we would love to see them!