Need 'logo page' before wordpress page!

Question

I made this website for my client using WordPress. It's all great but now he's asked me that when someone loads the website, before all the WP goodness, there's a page showing just the logo, then you click the logo and go to the main page.

I'm thinking I could either do this by changing WP's index to some other name and have the actual index file be the logo thing etc; or have a pop-up* on the actual WP index that darkens the rest of the page, then you click the logo and it's gone, allowing you to navigate the page normally. It would have to appear only the first time the user loads the page and not when you 'come back' to it from another page.

*Like when you click a screenshot here panic.com/coda for example.

Can anyone help me with either option or show me a new one?

Thanks!