That's good to hear about the labs then! About the dachshund being good with children, I'd get a puppy from a conformation line breeder, if you're set on the breed. It's much more reputable overall and you will have a MUCH more definite image of the kind of temperament you are getting, especially if you add that you hope for the most chill puppy who is okay with everything, including children... haha.
I'll go on a tangent and say that boston terriers are incredibly cool and easygoing. Much higher chance of getting a chill boston terrier who is good with children than taking chances on a dachshund... Boston Terriers are also incredibly hardy dogs in terms of playing with large dogs, besides their health problems.