Are UGG boots practical for outdoor Winter activities?

My wife has been admiring the UGG clic tall boots for several years and has yet to purchase them. Our anniversary is approaching and shortly after we are taking a family ski vacation to Colorado. I figured it would be a nice jester to give these UGG boots as a gift for our anniversary, so that she will be able to use them on our trip. The problem I have encountered is that the UGG web site claims that the boots are NOT waterproof??? I know these are popular boots, as she points them out every time we see someone wearing them but what happens if she wears them in the snow sledding with our kids. Or better yet what happens when we return to our home in Florida and she gets caught in the rain in them??? Is there stuff that I can can purchase to weatherproof them? Are these boots practical for outdoor Winter activities??? Any help in this matter is greatly appreciated! I would love to give her this as a gift but would like her to enjoy them without worry of destroying them!