Well I would normally recomend Kayako SupportSuite.
Its great, has many many features and the live support is really good - besides not being able to accept live support sessions from a web browser. Another good thing about Kayako SupportSuite is the 'LiveSupport' program, primarily for live chat sessions. However, it allows you to very easily see who is browsing your website, where they are on your site and where they came from.
However, this may be a bit too much for you since you're offering hosting for specific a CMS / piece of software.
Have you ever thought of osTickets, an open source ticket system. If your only planning on being small this may be enough.
I dont know how big your business is going to be though so dont know, for more general web hosting I would say Kayako though.