I have two littlies, and two older stepsons (11 and 14). We find that if the older ones get something we can often prevent the littlies from getting it, and vice versa if the littlies have something. It's a bit easier because of the age difference though and because the older stepsons are happy to isolate themselves in their bedrooms with their computers, lol.

If the littlies or I catch something, then it's hard to not to share. It usually ends up that myself, both kids and DH often get it.

To try to avoid spreading germies, I love glen20. I surface spray wherever a sickly person has been, lol.