Preheat oven to 375 degrees
Beat butter & shortening together in mixer bowl until smooth
Add in sugars - beat until fluffy
Add eggs - mix slowly until just incorporated
Add in pudding mix, vanilla, molasses, baking soda, water & salt - beat well
Mix in oats & flour
Roll into tablespoon size balls & place on baking sheet about 2 inches apart
Bake 12-13 minutes - or until tops look lightly cracked
Cook on baking sheet & then transfer to wire rack
Make icing by mixing eggnog & confectioners sugar in small bowl starting with 1 cup confectioners sugar & a drizzle of eggnog. You want just enough eggnog to make it dippable but not too thin that it runs off the cookie. I ended up making 3 batches like this to get through all the cookies.
Dip each cookie half way into icing & place on wire rack to drain
Sprinkle with decorations before icing sets