How much handling does the dream board have prior to being broken - is it hung up somewhere the rest of the time and untouched, or does it need to be handled throughout the show?
Velcro will be hugely obvious to the audience. Every night a great big RRRRRIIIIIIIIIIIIIIIPPPPPPPPPP will be heard by everyone in the space. Would not suggest.
One option if it needs to be durable would be to make it out of wood, and then use balsa wood biscuits/dowels between the two pieces. Balsa breaks very easily and it will give an authentic "SNAP".
If it is a quick "Rip off the wall, snap in two" and that is all that happens to the board, I would probably use XPS foam coated with mod podge and magnets with a sound effect if needed.