On your main VI's block diagram, go to each subvi's icon and check the "SubVI node setup" and make sure "Show Front Panel when called" is not checked. This is the option that will actually show the front panel.
The option you listed in your question (open frontpanel when loaded) only puts the VI in memory, but doesn't actually open the front panel for viewing.
I believe that is what you need to do, good luck with it, Doug