I'm surprised you had trouble freezing milk, we do it all the time - since all my housemates usually buy milk on the same day (we all get up, see there's no milk left for tea, then we all come home with some that evening...) so which ever one is opened first is drank and the rest frozen so it won't all go off before we get to it. We don't do anything special, just throw it in the freezer, the back in the fridge to defrost about a day before we'll need it. Just regular semi-skimmed milk.
anyway - what I really came along to say was how much LOVE the flying carpet!!! way to go!! such a cute idea, and I love the backing fabric you choose too