Inna,
Create a COPY of View On Demand Access Rights and then EDIT to NOT Allow VIEW (See screenshot below), call it CUSTOM_VOD_NoView.
No go to the Universe Folder &/or Universe and Assign Security to the Group and apply the new CUSTOM_VOD_NoView Access Rights.
This will allow the users to run canned reports against the Universe but NO see it the Drop Down list to create NEW Ad Hoc reports.
Regards,
Ajay