Let’s go back to the sightseeing analogy though. Imagine taking forty 7-year-old kids on a full-day tour of, say, London.
Before you got to London, would you prefer the students had some idea what they were going to see and do? Probably.
Would you like their parents to be informed about how they were going to spend the day? I guess so.
Would you take them to Picadilly Circus and say ‘OK, everyone! Listen up! We’ll meet you back here in 2 hours.’? Umm. No.
Might you consider giving them a map and some important contact details? I would.
I agree that in some ways the 40 kids might learn a great deal by being given a freer rein. You’ll not end up with forty of them though and it’ll be fun explaining to their parents why sixteen of them spent the whole day on the London Eye, ten of them sat in an amusement arcade all afternoon and only one of them stumbled on the British Museum by chance, spent two hours in the souvenir shop and then left without realizing where they had been. There were also the three that got on the train to Birmingham and the chap who sat in McDonald's all day eating chicken nuggets. I’m sure you can have fun thinking of other students in this scenario.
I have done a great deal of Dogme-like teaching. Actually it led me to become involved in creating materials. It works better the less students you have, the more responsible and individually motivated they are, the greater your understanding of the target language, the greater the students' language ability, the more time the teacher has to devote to preparation of attractive lessons and the less control the system requires.
Most young learner environments are heavily weighted towards the wrong end of these scales. That's not to say we should give up.
A well known ELT editor once uttered the immortal line in a karaoke booth. 'Sing something more Springsteenesque!'. I would say that all teachers should aim to be more Dogmeesque but you might find a decent coursebook comes in very handy on the journey. What a decent coursebook is is material for another day.