Falling down and getting up correctly is fun for pre-schoolers. I would start by asking them what they know about ice - it's cold, it's hard, it's slippery, etc. Point out that it's hard to walk on but that there are special shoes built just for moving on ice - and that when you learn how to use them, you can go really fast and do things on the ice that are harder to do on the ground. Then show them skates. Let them try on skates (maybe get a couple small sizes from rink rental) and take turns trying to stand in them. Then do the fall down- get up, stand on one foot, hop, etc stuff to keep them moving and giggling. Jump and try to turn around once in air (most can't do it.Finally see if you can show a video of a group lesson or a Basic Skills competition(USFS might have something) or read a book about skating. Show them a medal. Try to make sure that whatever you do includes boys and isn't focused only on the pretty glittery girly aspects. Emphasize the fun and the athletics and the health benefits.