The recent threads about obesity etc have got me even more determined to encourage healthy habits in my DCs (4 and 6). I think a lot of people on those threads want to do the same so I thought a specific place to chat might be helpful!
The biggest change we made last year was ditching the TV/DVDs Monday-Thursday. We'd got really dependent on it as a family but now the DCs just play more and don't even want to binge on it at the weekend anymore.
Active stuff I find hard, I'm disabled and am in pain and/or dizzy a lot, but thankfully DH takes them out a fair bit. We don't have a garden but we have lots of woodland nearby. They walk to school (no car).
We'd also got a little too reliant on freezer food over the last year or so and they were getting a bit picky about food. I have finally started being able (physically) to cook again and I'm trying to get a bit more variety and also get the DCs involved which we'd not really done before.
We are also saying no to constant requests for food. DH in particular hates letting them be hungry (grew up starving thanks to abusive mother) and has often given them snacks even just before dinner but I was really struck by the other thread where it was said by lots of posters that snacking is a totally new phenomenon, and it's ok to say "nothing til dinner or you'll spoil your appetite"! 
Anyone else want to join me in making things healthier for their DCs?