Terriers are just fine if you treat them properly. See my earlier post about how we've had them since just before our first child was born.
In general, they need firm but very kind treatment. With ours, we found that lots of handling worked best. Lots of cuddling, stroking, playing. If they start getting 'mouthy', shut them up in a kitchen without a word. That way they learn that puppy nipping does not get results. Every time they are gentle and loving, they get more and more attention.
The first two we had arrived at the same time, aged nine weeks. THey did a lot of their puppy play-biting on one another, which was good for us. The second two, who didn't arrive at the same time, tried, at first, to use us as their biting buddies. We just kept telling them off in very deep, growly voices, and sometimes shutting them in the kitchen if they repeated the transgression. On one occasion I scruffed one of the pups for repeated play bites. This didn't hurt her, but it made her think twice about trying to nibble my toes as I tried to cook supper.
By the time they were six months plus the pups were generally a lot calmer. Now, our latest terrier is 21 months. A real softie indoors. Loves rolling around on the floor with the children. On walks, she is a hunter-killer. We have to be careful where we let her off the lead: if we know there are likely to be rabbits or pheasants, she stays on the extendable lead. Her recall is good if she's not distracted by prey, but I never take chances. She will walk for as far as we want: twenty minutes in the rain, or for hours and hours. She loves ball games. Any job we undertake indoors or outdoors is supervised by her: she is unbelievably nosy.
In short, they are really good fun dogs. With strong senses of humour. I love the fact that they are so portable, too. Even in a small car.