I've got 5 Dc. 14,11,7,5 and 2. Without realising it, I have followed the 'calmer easier happier parenting' approach. I didn't read the book until I was looking for something to help a friend. My children are very well behaved at least 95% of the time. In fact, the way I would describe them is cooperative.
I refuse to raise my voice in public unless it is to stop immediate danger, like traffic.
I explain expectations when we are going somewhere. For example, on the way to the dentist I will say that we will be sitting quietly, speaking quietly, waiting patiently with no fidgeting. I remind them about their manners and as we go in I finish with, don't let me down.
Then when we leave they get a run down of all the positives. For example, great sitting DC3, you were very polite DC4. Thank you. You should be feeling very proud of yourselves. They don't get a reward. Good behaviour is expected. The reward is feeling good.
A 5 and 7 yr old absolutely should be able to sit in a café for 30 minutes with near perfect behaviour.
It works for us. It might sound like I am on their case all the time, but they are left feeling positive about themselves. They use phrases like, 'I'm a helpful girl', 'I'm an independent boy', 'I'm a hard worker'.
The great thing is the eldest dc now 'coach' the younger ones. They encourage them to sit nicely on the bus etc and set a good example. I am often complimented on their behaviour in public. I am shocked by some of the behaviour I see from children, but it's just children doing what they are allowed to get away with.
It is hard work and I find taking them out exhausting because I am forever 'on', offering praise and recognising every effort towards behaving well, but it is worth it.
Children are so different though and maybe I have no idea and it is all down to luck! It makes me feel better to believe I have an effect!