It's only one state away, so not a cross-country flight or anything.
Freeze it wrapped in at least one layer of plastic wrap and then a layer of foil. Keep it frozen until right before you are ready to put it in the shipping box.
You could use this technique for wrapping the outside foil: How to Wrap a Quickbread
Since your uncle lives in a next-door state, you don't need to use dry ice or anything like that.
Use a shipping box bigger than your pound cake. Line the bottom with a lot of tightly crumpled newspaper or packing material of some kind. (You don't want your pound cake to be bouncing around in its shipping box.) Then pack the sides tightly with same stuff... and then pack the top. Ship immediately, using priority shipping, so that it doesn't sit around for 7 days in the Post Office or wherever.