As far as I am aware, you have to either hide them or lock them, you can't do both, so if you want them locked they will be in view but not accessible. You could change the folder name to something like "settings do not open", but imho its a waste of time as you can still see in folder BUT cannot access them.
I take it you have gone into youth protection setting and set password and locked them.
So try going into bouquet editor and hit the dbox key until you see hide (blue button) then make sure there is no eye with an X across it beside your adult bouquet, then hit dbox button again and blue button becomes lock and has a key beside bouquet. then exit and press red to save.
btw...i may be wrong about hiding and locking together, but it may at least lock them