Or, from another perspective...
perhaps the dogs perceive the children as "aroused"...now that's a horrible thought.
Quote:
"Oh my word, what is wrong with my dog, they are humping and they've been fixed." As far as mounting (aka humping) is concerned with neutered or spayed dogs, observations have shown that those (mostly males but sometimes females) who are aroused or excited often times exhibit mounting behavior.  This is referred to as a social overture during play. It is believed to have nothing to do with dominance or with one animal trying to convey something to another.  Latest research has shown mounting to be a normal canine response that occurs commonly when dogs, especially adolescents, experience emotional states of arousal.
The key to prevention is teaching a dog skills like come or sit/maintain. For example if the dog is going into a state or arousal, they can be cued to stop the behavior and calm themselves down before mounting occurs.  With the skills you've taught your dog, you will be giving them something else to do besides mounting.  In the event mounting occurs you may need to interfere, but do so very carefully so you do not further arouse the dog or cause the dog to feel threatened.
When mounting is occurring, if you are concerned that one dog is getting annoyed and can not defend themselves or get away from the humper, step between them and separate them with your body.  This is only if the dog has not been taught skills with distractions, and is not responding to your cues.  If the humping dog can not calm down on their own and is bothering other dogs, crate them or pull them aside and wait until their arousal level lowers.  If the "humper" is not particularly bothering the other dogs - let 'em go for it. Look at it as mother nature's way of giving them an opportunity to practice for sex.
There is evidence that some female dogs exhibit "male" characteristic
s, such as marking and mounting, which is believed to be associated with higher levels of testosterone.
Researchers are tossing the whole dominance theory and rank reduction stuff to the wind. The most recent thought is that humping is simply a social behavior/motor pattern that dogs have. All it means is that the dog is excited or in an aroused state (they are hyper). Females do it too. Dogs do not understand rank because they do not relate to the experiences of others. They are self aware but not other aware. They can not understand "you lose, I win." All they relate to is the present (this feels good) and the past (this was reinforcing and felt good before).
Dogs live in the present, but bring their past experiences along with them to determine how they will respond to present circumstances and situations. Â What they cannot perceive is the future or how to control or influence the future.Â
Another dog's play style may be too rough for your dog and could end up getting one of them in trouble.  A dog's play style cannot be changed. If you are concerned with another dog’s play behavior, you will have to manage your dog and only allow them to play with dogs that have mutual play behavior.  You are taking a chance every time you let your dog play with an unfamiliar dog because that unfamiliar dog may misinterpret your dog's behavior as threats rather than as play.
Article Supplied by:
Gina Micciulla
Owner & Trainer
Educating Humans Teaching Dogs
http://www.thepetprofessor.com/articles/article.aspx?id=1878