I will try to get Demo 7 on the DSi and Wii this weekend. It looks like the Wii won't be much of an issue, but the DSi browser may not be able to handle it, due to bugs in the way it treats dynamically-generated page content.
Demo 7 is a one-player rewrite of the PvP demo with bugs fixed and other aspects greatly improved. Demo 7 pulls actual stats, items, etc., from the database in real-time, allowing constant updates. The PvP demo was all just static content.
To play the PvP demo, you need to enter it the same time someone else does, or it will time-out.