I have 4 kids and am a single dad. One thing that always helped with my girls esepecially (they share a room) was to award them reading time at night. If they were quiet, settled, and in bed, they could keep a small light on for 30 minutes to read, look at a book, or sometimes even color (though I then had to hunt crayons out of their beds). The deal was that "quiet free time" was a privelege, and any disruption to tonight, both ended quiet free time and cut out all or part of tomorrow's time too. We made a big deal out of it, as it was a "big person" thing to do, reading before bed.
As they have gotten some older, I take time to spend at least 5-10 mins individually with them at night, talking about their day, what they think they might dream about (my favorite), and how much daddy loves them. Then we say their prayers and say good night.
Just a couple ideas. All in all the bottom line is there has to be consequence to their not following bed time rules. The consequence has to mean something to them, it has to hurt.