I would say, for now, just be a positive, fun, balanced influence on your kids. You must feel such a loss of control over this religion messing with their minds. Let them know they can make their own choice later. Keep it simple of course, but let them know this basic thing. Also, I try to teach my kids about advertising, and how companies are trying to get them to spend their money and how manipulative they are being. Without discussing specifically the religion, teach them these techniques. 'See in this picture how they are trying to make these people look SO happy, so you want to buy what they are selling? Is that realistic?'
I hope that helps. Also this : Of course set limits, but be the fun parent. When they're with you, do the fun stuff. And Make sure they have friends that aren't witnesses. That's huge.