How to run a guest network with a Windows Server as DHCP?

I got a very small domain network running of a Windows Server 2008 R2 Foundation and we get to a point we would need a wireless network for our guests to be able to surf the Internet. I don’t want to just enable the wireless access point and everybody with the password for the wifi being able to look around in my network.

I would like to be guided in which way to look. I’ve seen a lot of post about NPS but I don’t quite understand what I need to do.

My DNS, DHCP is running off my AD and a little D-Link router is my gateway.

Thanks for any advice