You can do it manually. Just pretend your going to install gnome-games, and write down all of the dependencies that the package manager says it will need. Then while your at school, go to this site http://packages.ubuntu.com/
, and download gnome-games and all of it's dependencies. You will have to download them one by one. This is a pain in the butt. Linux distros use different versions/package names. It is almost impossible to make a software package that will universally install on every Linux distro. With Microsoft, you only have one flavor to make a package for, so one size usually does fit all. There are sites that you can download software from for linux, but you also have compile them from source, and install all of the dependencies that package requires. The package manager is like Majorgeeks. Just tell it what you want, and it will download and install it for you. A DVD repo will let you install games and anything else you could think of without downloading anything. It is all there on the disk. Mint is not yet supported by Wubi.
"The only thing necessary for the triumph of evil is for good men to do nothing." Edmund Burke