Stitchnripper- I make a lot of frozen yogurt & ice creams too. All the reading I've done for making them suggest 1 teaspoon to 1 tablespoon of vodka added to the machine just before it is finished freezing the mixture. I have tried it & the vodka doesn't affect the taste but does seem to inhibit any ice crystals from forming & keeps it slightly soft.. I will also put glad wrap right in top of the ice-cream & pat down snuggly to eliminate air. Go one step further as well & store near the back of the freezer so that it doesn't warm up every time the door is opened. All in all- that helps my treats stay fresh & yummy with out a stale taste or hardness. I do admit though that it usually doesn't last long enough to form the crystals!!!
Might be worth a try even is you need to 'borrow a teaspoon' of vodka from a neighbor!!! That ought to get them wondering!!!
King Arthur flour had a special container for storing ice cream, but don't know if they still do.
Good luck
sewverybusy1