Hey euro foxy,
Depending on the location of the 'cracks' you could either tape across the hinge or simply glue the crack. If it is broken on the hinge you can buy hinge tape or fibre tape, but be sure to tape it so there's still flex in the joint. If you need some advice about that please ask. If it is broken across the actual surface then glue it first with foam safe CA before repairing the hinge. Balsa wood ailerons will need to be fairly well made as different thicknesses might affect trim and other control.
There is my bit for you to ponder anyway...
Hallmark