Fortunately the information sign at Heads Road Park Orchards is out of date. The Mullum Mullum Trail continues on to Park Road. It was the last section to be completed, finally opened in 2018. The project was on hold for some time because of the construction of a sewer main in the same space and this work had delays.
A photo from bicyclenetwork.com.au shows the last of the prefabricated bridges being lowered into position. No small structure it is the first bridge found immediately after crossing Heads Road.
This is a beautiful and quiet section of the Mullum Mullum Creek. Most of the trail is on boardwalks, passing lots of big trees which were being enjoyed by noisy galahs on the day I walked on through.
The creek itself is lovely, it twists and turns around and over natural rock forms.
I took a short video which include the birdsong that adds to the enjoyment. You can find it here.
Some of the houses in this valley have been here for decades and blend into the bush. Nearing Park Road there is a fence and gate. This is the Whitefriars College, the second of the private schools that are on the creek.
The trail runs up the hill along Park Road to a safe crossing point. Along the way it is hard to ignore the huge white house that also dominates the last section of the valley walk. While it is architecturally interesting it is a pity it is not more sympathetic to its surrounds.
skippingstitches 
Another beautiful natural section of your trail trek. Yes that white home does not blend, perhaps it should have been painted a different colour. We are so grateful that we live with beautiful nature surrounding us.
It is nice to see the context of that video. Beautiful and soothing!
The house doesn’t seem very much in sympathy with its surrounds. (It also looks more like an office building than a house). Maybe once it has gardens around it it will be less intrusive.