Hi Sue,
Yes I have seen Razor Shells at Lake Macquarie and Port Stephens too. Wouldn't a good pair of booties protect you? (not the thinner sort, but the slightly thicker type of surfing bootie)
I always try to slow down to almost a stop before getting off the board and try to disturb any sleeping stingrays by making surface noise. If you can see the bottom it is a big help, if you can't then yes you have to be very careful, especially if you don't know the area.
Where I sail mostly, the Gosford area, there are no Razor Shells but there are plenty of friendly stingrays and sea-turtles. They usually keep their distance if they know we are there. When you surprise them, expect a bad reception. I have had them come right up to my feet while standing in the shallows and never had a problem, but I am not complacent about the risks sailing with these creatures. The rays seem to like the sandy areas but do blend in very well.
As an extra precaution we always push our boards out in front of us as we wade to the deeper water. This works. One of our crew has actually had his board punctured by a ray, leaving a nice hole in his deck. Better than in his foot for sure and easier to fix!!
) but nothing likes being stepped on. 
