I read the book Baby Wise three times and it did NOT work for me!
Suggestions: Keep the same bedtime routine every night - very important--e.g. dinner at 6, bath at 7, read book at 7:30, prayers and bed at 8. I would stay away from music, because that might even be stimulating them. One of my children doesn't like a lot of noise or music when she is tired. We have three children and crying it out just didn't work, because no one would get any sleep.
When your children nap, let them sleep as long as they need to and make certain it is early enough in the day, where it doesn't interfere with your nighttime routine. With three kids, I didn't have a set nap schedule, but looked for signs when they were tired. Sometimes their nap was longer than others, or earlier than other times. But I was a stickler regarding bedtime. I started dimming the lights around the house and they got the idea that it was approaching bedtime. The dr. told us not to lay down with them because if they wake up in the middle of the night, there will be a void (you not there). Every child is unique and individual.
Our oldest stopped naps altogether before she was two. I had tried everything and it was a waste to even attempt a nap. Your children may even be phasing out naps where they don't require a nap every day. Every child is unique and individual. No matter what all the books say, every child does not fit neatly into a particular category or set of guidelines.
Good Luck! Hang in there.