Male with dog walking in the park, not very far from what you're describing here I guess. Extra points if the dog is fluffy.
“I thought Fangorn was dangerous.
'Dangerous!' cried Gandalf. 'And so am I, very dangerous: more dangerous than anything you will ever meet, unless you are brought alive before the seat of the Dark Lord. And Aragorn is dangerous, and Legolas is dangerous. You are beset with dangers, Gimli son of Glóin; for you are dangerous yourself, in your own fashion. Certainly the forest of Fangorn is perilous — not least to those that are too ready with their axes; and Fangorn himself, he is perilous too; yet he is wise and kindly nonetheless.”
The children correctly assess you as "dangerous". They then assess whether you are wise and kindly, and find you so, making a good ally or friend. Merely wise and kindly people do not make as good of an ally or friend.
A Golden Retriever will on the other hand project friendliness. There are small dog breeds like Yorkshire which are rather aggressive, but in my perception they wouldn't increase the threat perception.
These are of course stereotypes, they won't be true every time, but are IMHO useful as a rule of thumb.