RSVP Pro is all about inviting people to events, recording attendance/taking registrations/payments and sending event reminders. There are demo videos of the key features available here http://www.jevents.net/downloads/category/62-rsvppro_12
Would the restaurant's customers be registered users of the website?
We do also have a managed people addon for JEvents which allows you to create entries for people (or resources) of different types. Including images, addresses, URLs and other custom fields. You can then associate these 'managed people' with events.
BUT this is designed for things like managing speakers at conferences or musicians performing at an event etc. i.e. most of the details of these managed people are expected to be public and would appear on a website. Its not a private address book.
After you have taken a look at RSVP Pro perhaps we could continue the discussion in the gold member forum.