K.C.
Ok that's just ignorant. I'm a dog owner too and that's why I have a dog run in my yard because I don't like to pick up dog poop, I let the lawnmower take care of it. I don't think you can say anything now because it's past but what I would do is throw a couple poop bags in the tote you take to the park and when you see that happen again, walk up the owner of the dog politely hand her a bag and tell her you just happen to have one handy since she obviously forgot hers. If she gives you attitude you can simply say that it's a health concern. Your children come to enjoy the park and you would prefer that they not be exposed to animal feces. If she still doesn't get it explain to her that she's leaving you no choice but to contact the authorities (isn't picking up dog poop a law?) and then do just that and let them handle it from there. I'd be livid if I were you so kudos to you for keeping your cool and finding a diplomatic solution.