Wireless router with login page and approval

I have Sonicwall firewall and to provide wireless connectivity to employees, I just utilized an old 802.11 G home router connnected to Sonicwall. Routing is disabled from the wireless router to LAN, it's just to provide internet connection.
Often I have to give password to visitors and others to access internet through this wireless router. But I can't disable this password feature because I don't like to leave it open for all. What wireless router is recommended to serve this purpose?
For example, I like to provide a login page to users accessing, then they type simple personal information and in-house person who knows the user approves the access, then the user is good to go to internet.
Any recommendation?
Also, I have three Access points connected to the wireless router for dead spots. All security feature is provided by Sonicwall, so I concern less about this feature of the router.