My place is about a 5min walk from the wahroonga village, so nice and handy for me.
The old road between Horsby and Mooney Mooney is still fine, drove it the other night. Not sure if the limits have changed but you can have a great drive without having many issues (much fewer than on the F3 anyway).
Perhaps a plan of action would be F3 up to Berowra (cuts out all the lights etc running up there on the old Hghway), old highway from Berowra to Mooney Mooney, back onto the F3 to the 2nd Gosford exit then onto the Enterance. 1st exit for Gosford to the Enterence from memory isn't as much fun.
Still either way it should be a good day out.