DNS is not what you want to do for allowing other people to upload. You would use DNS to point a sub-domain of your site an other hosting server, or to set all E-mail to be sent to your own servers. adding a DNS entry won't let people access their parts of the site, but you could set it so they would have to have their own servers and host their part of the site locally.
A CMS is one possibility to do this, also you can look into direcotry remapping for users. With dreamhost only one user has access to the files associated with the domain. So you can share that one user/pass if you want. Or with direcotyr remapping you can set up users, and remap a direcoty they can access to be part of the domain.
Alternativly, you could set up subdomains for each campus, and give each one a different user/pass.
If you're determined to go on with the DNS settings, which you really shouldn't, check out this wiki article And this K-base article