Boarder Collie meets and exceeds many roles you want from a farm dog.

A well trained one can help in many ways around a property.

This.  Look for what will be an obviously larger puppy so it's not so fragile.  Mutts have far fewer health issues as a rule because their questionable parentage gets rid of the problems caused by inbreeding the popular purebreds to death.

ANY dog requires socialization or has the potential to become aggressive, a fear biter, territorial, etc. Even the gentler breeds.  Some dogs, of course, require much stronger handling, and if you get a dog that is territorial by nature or has a strong protective nature bred into his/her line, the need for socialization and training really shoots up if you're going to prevent having a problem when he's grown up.  Cute puppy behavior (read 100 lb dog jumping up on a 100 lb woman) sucks when the dog is grown up.  If you choose a rottie, or another extremely loyal, loving and intelligent but stubborn breed, you're in for a lot of work, but a lot of reward.  Sounds like the ridgebacks might fall into that category. I've had limited experience with that breed.  It's not "my" dog if that makes sense.

ANY dog will know when somebody is up to no good, and most will protect your kids if necessary.  Not all. But most.

The labs are always a good fallback.  Gentle by nature. But they can be real pains in the ass if they're not taught to behave, and they get big.  They can also get passive aggressive. No, they won't come at you full-frontal attack like a GSD or rottie.  They'll wag their tails, then sneak up on you from behind.and bite the shit out of you.

I'm a dog lover, and have trained dogs for SAR for a lot of years.  But I'm pretty anal about every dog being taught who is alpha animal in the pack (you and your family) and taught proper socialization, even if they're just gonna be a farm dog who sleeps under the porch.

There is no one perfect breed.  Every good quality has a flip side, like a coin.  My experience is that you get the best out of a dog when the dog is part of the family, but is taught the rules from the time his/her eyes open (which means as soon as you get the puppy.)  

But I personally don't think little bitty dogs work out well in a farm/outdoor environment.   (I know there are a couple of exceptions to this rule.  But even most of them have been bred for profit and show, to the point of losing all their stamina and better qualities.)  

Mutts are the best dogs. I'll say that after years of training purebreds for SAR.  I love those breeds but I know what it takes to become the alpha and stay the alpha with those breeds in most cases.  Most people won't put in the time and don't realize they have a problem until it's too late to fix easily.

Yes, I do have a problem with the number of animals we euthanize in this country just because somebody didn't want them or didn't bother to train them while they were little so couldn't manage them later..  But even without that concern, Mutts are (usually) the better animals. YMMV of course.

I'll hush now.

Good luck with your dog hunt and let us know what you get!

Yes, when they grow up together, they really bond.

We have a dog that was trained for SAR but is retired now, and he's taught to not be aggressive toward anything, and ours are not allowed to chase and/or kill small animals EVER.  (That prey drive is bad for SAR work but also I just don't think my dog should be chasing and killing things that aren't doing me any harm but that's just me.  You wouldn't believe how hard it is to find chew toys that don't freaking SQUEAK. )  Anyway...because they're not allowed to chase  and go after animals, we never have trouble introducing new kittens/cats into the family.  But it is MUCH easier to do as you do and raise them together if life allows that.