Hi Linda You could divide that Shasta daisy this fall (September). If you don't have enough time this fall, it could be done in spring also.
As to the mums, you can do it either way. In areas that get very cold in winter, the foliage is often left on to act as a "snow catcher". The snow then acts as an insulator. If seriously cold weather is not an issue, the foliage can be cut down in fall.