Whenever I design for a family, I automatically choose plants that aren't poisonous to dogs if they have dogs, or kids if they have kids.
But I always use plants that are poisonous to cats...but that's just me. 
Just kidding. I'm here all week.
Seriously though, whether what I do is what ought to be done or not, it's just something I try to do. I'm sure I'm not as strict about it as it sounds, and probably forget often enough.