how good is to divide groups

Reading about this topic in programmers exchange, I assume that maybe small groups would communicate better but some projects might be a bit bigger so you need to create a module for each team and focalize what you have. Still who will lead the group would have to create a methodology so developers could giveback with no overpressure. I think is good to be inmerse in UI and BL both so you would have a better understanding of the solution, but sometimes, when a developer is more skillful in one area than the other(design) you probably would have better results focusing people on what they feel more comfortable.

On meeting for developers

A few decades ago, "Datamation" magazine ran a short article on "how to hold good meetings".

Three points they hit are extremely important.

1.

Have a WRITTEN agenda, circulated to everyone well in advance of the meeting, and KEEP to it.
2.

The meeting must be chaired (run) by the highest-ranking line manager present. Reason: He/she will run it anyway, so you might as well make it official.
3.

Whenever possible, limit the time to NOT MORE THAN ONE HOUR. If, as the one hour mark approaches, it is clear that more time is needed, the only topic you should be discussing is when and where you will reconvene, and what action items must be accomplished before then.

There has been a HUGE amount of research on optimum meeting lengths. Every study has shown, very clearly, that people's attention and energy drops DRAMATICALLY after about fifty minutes.

Another point should be mentioned. If Joe doesn't need to be there, DON'T MAKE HIM ATTEND. Send him a convenience copy of the agenda, send him a summary if he needs to know the results, but, if he isn't an active participant, don't waste his time.