Guide to how much space WiiWare games use
Kotaku's posted a handy guide showing you just how much memory each WiiWare title takes up. Your machine has 2163 blocks of memory built-in, and the games take between 100 and 300 blocks.
WiiWare launched on May 20 in Europe. Hopefully by then you will have worked out which games you plan to allow taking up a big old chunk of space on your Wii for any length of time.