Cyn, do you have any meringue powder? If you add a little to your regular
butter/sugar icing it helps it firm up a little. My sister just uses her plain butter icing but allows the cookies to stand out in the air until the icing firms up before packaging in her cookie trays at Christmas. This proved dangerous a couple of times when her one large dog decided to counter-surf. I think she started spreading out trays on a bed in a spare bedroom that could be securely closed.
Another option would be to just freeze as is and finish up with frosting after they are thawed. Sis makes many cut-out sugar cookies for a couple of months before Christmas, then frosts and decorates them the last weekend after thawing them.