To star or not to stat.
I often use a combination of ground plane and star. In the case of a dual power supply, I might pore a ground plane around the LM7806 and a different around the LM7906. Then connect the two together at the output jack. Any time you have two different circuits it is OK to keep them separated and then connect them at one point. I can't see what you are doing! This supply is so simple I think you can do what you want. A good healthy ground never hearts. I would use ground across as much of the board as you can.