If your fernleaf peony is large enough it can be divided, although peonies resent being divided frequently. The basic steps in dividing peonies are the same as for other clump-forming perennials. Those steps are outlined in our story on dividing perennials at http://www.bhg.com/gardening/dividing-perennials. Make certain that each division has healthy roots and several ""eyes"" or growing points. Immediately replant the division that you will be keeping, placing it at the same depth that t was previously growing.
You can wash the soil off the division you plan to send to your son, but keep the roots moist by packing them in moistened shredded newspaper, moist sawdust, or moist sphagnum moss and loosely wrap the root ball in plastic. If you're shipping half way across the country, use a package delivery service that will guarantee delivery within 2 days.