I think I'm interpretting your question differently than Matthew, but I believe the answer is that you can leave your sheets hidden. The dashboards and navigation should work fine with hidden sheets. You will need to check the show tabs option when publishing to be able to navigate. And navigation will be limited to any visible sheets/dashboards (so you wouldn't be able to have an action go from a dashboard to a hidden sheet, for example). But navigation from one dashboard to another visible dashboard (even when it contains hidden sheets) or other visible worksheets will work fine.
Yes, I misread the line: In my workbook, I have hidden all the sheets and only the dashboards are displayed.
As Joshua clarified, when publishing, you'll need to show tabs in order to navigate between visible sheets/dashboards.
Sorry for any confusion.