I am doing a photography website using flash. What is the best dpi and way to save scanned photos for Flash so that the photos look very high quality?

I usually scan photos in a 300 dpi. Sometimes higher, depending on the size
original image. Then I open each image in Photoshop and reduce the resolution
in the Image Size window from the Image menu. I do this in two steps, first to
150 pixels/inch, then I use the Unsharp Mask filter to sharpen the image. Then,
reduce the resolution again to 72 pixels/inch and another unsharp mask filter.
I may change the physical size of the image at the second resolution reduction
to keep the image as large as I need it to be. I then save the image as a .png.