Okay, I'm back. We were out all day and the kids wouldn't leave the park until sunset and the mosquitoes were eating them alive. I tried to post earlier but autologged (kid interruptions) and lost my previous post.
Thank you again for an official reply. I really didn't expect one, and I'm grateful for it. Thank you!
We tried Internet play. Last night we couldn't get it to work, because apparently Runic's servers were down (?) but tonight it works just fine. It's a little laggy. We're on the other side of the planet, and it seems really silly to connect to Runic's servers to play the game with someone a few feet from me.
Our setup is thus: I have an old Win XP computer. My husband has Win7. We have had some minor hiccups in the past with local networking (namely, sometimes he can't find my computer's shared folders). Win7 seems to hate XP a bit. That's okay, I don't like Win7 either, that's why I don't have it.
We have a fiberoptic modem with a hybrid router. The computers are physically plugged into the router while it broadcasts a wireless signal for the tablet PC and the Wii. The router is a Buffalo (I don't recall which model exactly) and we've never had any problems with it. We have had problems getting the DS to work with it, I don't recall exactly why.
I can dig up the manuals and model numbers for the router and modem, but the latter isn't in English... at all... so it might be a bit difficult for me.

I can read it... and its network setup page... very... very... slowly. Like less than Captain Kirk speech speed. Definitely less.
Anyway, thank you again.