We have a Parson Russel x, got him from a rescue centre.
The centre were really good - they obviously can't tell the temperament of any dog in kennels, so they have a scheme where you take the dog home over the weekend, and 'road test' it, to see how well it settles. You can keep it for a few hours or a couple of days.
Dennis was supposed to go back on the Sunday, so that he was ready for a castration, but we didn't have the heart to let him go back into kennels.
He's great with DS - really tolerant. But he knows the difference between an accidental poke in his eye, and a deliberate yank on his ear.
My MIL has a chocolate lab, who's fantastic with kids, but this is becuase he came from a home where he 'grew up' with young children. He was a 2nd dog, and the 1st dog decided he wanted to be the only dog, and acted aggresively towards Coco.
This led to the owners looking for a new home, and they offered him to my MIL before sending him to a rescue centre.
There are rescue centres who take in dogs like this.
There are labrador rescue centres and greyhound rescue centres which are always full of nice dogs looking for good homes.
I'm partial to greyhounds, cos they need only a little exercise each day, and they're really quiet round the home.
If you contact each centre, and explain what you're looking for, and your living situation (working hours, how many kids, garden etc), they're sure to point you in the direction of a suitable dog.