
The only solition now would be to fence part of th garden as a no dog area so that the kids can play where there is no poo. I did this with my first dog, and have kept it that way as it is easier to pick up in a smaller area.
I would expect it would be quite hard to retrain your dog to go in a specific spot as you hadn't done this initially.
the posts are for dogs (male) to pee up aganst so hopefully lessending the marking of walls and gateposts etc, not for pooing or bitches :D