You need to set up the auto-answer feature of the modem, so that when you dial them, it picks up. Then you probably will need to figure out how to handle PPP setup.
An alternative would be for you to give them a second machine running Linux - then you set up the Linux box to do the routing and Win98 just talks over ethernet to the Linux box.
RAS still has to have them dial out, I believe. I will look into it.
I used to have a linux box router(Freesco) but got rid of it when I got DSL. If I put it at their house, it would dial me, ....again wrong direction. If I could fix the Freesco box to answer instead of dial out, you may have something. My problem is I can't spell linux. I'll have to go back through the setup to see if it can answer instead of dial out. If so,.... we have a winner!