I am in USDA Zone 7a/b. You could dig up a section of each clump and pot them up in plastic pots (get from Amazon) and put them at your son's place. Place them near his house, preferably on the west or south side. They will enjoy the moderation of temperature from the heat given off from the house. Make sure to get an appropriate (2" larger than the diameter of the pot: 10" saucer for 8" bottom diameter pot) saucer for each pot. Have him watch the water level in the saucers. When the saucers go dry, fill them up again. That will keep an ideal level of moisture in the pot. In Spring (later April) move the pots to a location where they will get full sun if they do not already get that.
This will keep them in good shape indefinitely.
