So essentially you're offended at the idea children should want to run around a nice big sloping field!? The fact is a lot of dog owners using that park are less responsible than you. I and my little boy walked past two lots of dog poo on the landscaped slopes in front of the sunken garden on Sunday morning.
Anyway why should that lower field - the only largish green expanse in the entire park - be set aside for dogs at the exclusion of children. Any kid would love tearing around that nice big sloping field. The other little pockets of green in the park are just that. Not big enough - especially when the sunbathers are out. Frankly, it's a bizzarre inversion of priorities in an otherwise child-friendly institution.