If you are looking for pictures showing how could be your flight experience, one of the largest online resources is Flight Report (click here). Most reports are written in french, but it's intuitive and an English version is available too here (but with fewer reports). You can also find many videos of the new cabin on youtube. Also find a nice and clear report here.

Onboard Brussels Airlines A330 (with new cabin) 1A, 3A and 5A are blocked for Miles & More elite members. They open up to all other passengers between 72 and 24 hours before departure. Start monitoring three days before.

The map already shows you which seats are close to another, I'm not sure how it could be clearer or how I could be more helpful than the SN website map or Aerolopa here. If you want everyone in your group to sit as close to each other as possible : try a middle seat combo, like the 2D 2F and 3D 3F combo and if some of you want to try a throne seat, try something like 1A 2A 2B 3A combo.

In any case, this cabin is not bigger than a large living room, you will never be too far from one another, you will all be together and happy. Enjoy the flight and don't worry too much !