We picked the friendly pup out of the litter too mainly because it came to us and it let my baby boy force it onto the ground and give it a bear hug and it wagged it's tail the whole time.
We had our heart set on a bluey but the blue pups seemed uninterested in us.
I used a guide dog temperament test when I got my pup home and he passed all but the retrieving test (at 9 weeks old).
Normally I wouldn't want a dog so placid but I have a child almost 2 years old so I didn't want to take any chances. The people we got the dog from were happy for us to trial him for a week and bring him back if didn't work out.
My 4 year old daughter would most likely be OK with the pup in question in this thread as she is old enough to get out of the way and she has no fear, but with a 2 year old it's a different situation.