Send form only for logged in users

Hi, I’d like to customize a WP site for customers, so that they need to be logged in to be able to send forms with product request, so that the forms include automatically information of the user (his/her username) along with number of product units.

The form should not be accesible for visitors not logged in, so that there are not “false” invoices.

I’m using contact-form-7, but I do not know if it is possible to include the username automatically.

Any idea, or suggestion about how to, or any existing and useful plugin?

Besides I would need, somehow to restrict anyone from seeing the site, indicating that they must log in in order to view it.

Thanks beforehand.

If it can help you, you can visit the under construction site here to get a more accurate idea:

Here is the home, that should be available only for logged in customers:

Here is a page with a form that should send the username automatically.