DD-WRT redirect HTTP to infopage before user can surf

Hi, I have DD-WRT v24-sp2 (10/10/09) mini on my Linksys WRT54GL. I run a open WLAN so anyone around can connect, surf and check mail. I want to setup an infopage with some info regarding terms and some links. I can make the html of this page, but I need assistance setting up the redirecting. I want new users to be automatically redirected to this site before he or she can surf. Once the page is loaded the user can reach any web site desired, I do not need checkbox for agreement to terms or anything. But there should be Continue button to proceed to the initial web page the user tried to reach. If possible, the custom redirect should only be valid for internet browsers. Not preventing users from reaching Apple Appstore on iPod/iPad/iPhone or email in email clients. The redirect should be displayed on WLAN only if possible, not LAN. There should be option to ignore some MAC addresses (for my iPhone and PC in example). Please advice :)