Animal crossing is high on my list (assuming I can get the n64 or GC version running on linux) Freddie The Fish is on the list for both kids already.
I think Plants Vs Zombies was a problem in the past, but I don't know if it is *still* a problem. I'll look in to it.
They loved Kirby the one time they played it.
Bridge Constructor looks really interesting. It might solve the Sandbox Simulator want without leading to compulsive behavior. I'll take a look.
Thank you!