Is everyone just adding text to certain sections of the website or are they actually helping to build the website? If they are just going to add or change text from time to time then a simple CMS solution would work. Each person could have a login and access their sections or even access all of the sections depending upon permissions given in the php script. I used a couple of different solutions to allow a user to change her own text area and the easiest one if I remember correctly was one from phpjabbers.com called SimpleCMS. It costs a few dollars but it might work for you. I don't have any affiliation with phpjabbers by the way and I know that there are other scripts that do this same thing so I'm just throwing out there what I've used in the past.

Actually, SD is not even a website design tool, it's a website builder.

Requirements ------> design-------->build (SD) ---------->test and publish.

It's a pretty good tool, but has a steep learning curve for casual website builders.
SD is not meant to be a CMS, but with some tweaking it could be used to build a foundation for a simple CMS driven website.