GoblinGranny - I have to deal with other people's children despite having a miscarriage - i don't want to deal with that either but I have to. Dogs are part of people's lives and families. That's not for everyone, but neither are children. Dogs in general sniff, that's just what they do. It's like trying to stop a child talking, would you think it unreasonable to ask all children to stop talking because you don't like it?
The OP hasn't bothered taking the time to tell the owners that her DC are allergic/scared whatever. Sounds like the OP doesn't really like dogs anyway, she basically wants dog owners to keep their dogs on the lead so they don't go near her precious children when in a shared garden. If she won't take the time to explain to the dog owners (who are her neighbours, not strangers) that the dogs shouldn't approach the children, then she is being unreasonable too. The owners probably have no clue its a problem, considering she hasn't objected before.
Now in regards to dog mess, yes that's very wrong and the owners should clean up after themselves. Other animals such as foxes, birds will shit over that area anyway so let's not pretend that the ground would be nice and Detol happy if the dogs don't exist. And again, if this is in a communal area where dogs should be on leads that needs to be dealt with.
Not all dogs get up and close in people's faces, in fact all of the dogs I have owned hate it when people get close in at face level. In the seldom event, my dog passes someone they have a sniff and then carry on walking with me. In my experience it's normalky children who approach my dog, ending up getting too close at face height and end up hitting it in the face trying to 'stroke' the dog - in my experience it's the dog that should be scared of the child not the other way around.