That depends on your definition of "Need". WCS will allow you to do a lot of things like the ability to locate a single client or rogue device on a map. Very valuable feature. It will also allow you to do detailed reports about client usage on the network as well as RF statistics in an easily read format. Personally, if you're spending the money for 30 APS and a 4402-50 then I would get the WCS. My experience has been that once a wireless deployment takes off other sites will follow. I strongly suggest a separate WLC for each sites with WCS centrally managing from a corporate data center.
Note that if your network relies on a single WLC, then if that controller fails your entire wireless network goes down. It also means that you cannot lab-test changes to your networl; every change you make immediately affects all of your users.
Which is to say that a second controller is recommended for almost any deployment I've ever seen... and if you have two controllers, a WCS cuts your workload in half.