These are our two cairn terriers. They are small (approximately 8 kilos, so you can actually carry them if you want), funloving and well tempered and they don't shed at all.
Although I like the idea of visiting a shelter my own preference is to buy from a good dogbreeder, so that you know its history.
A lot of dogs, especially the very popular kinds, have been overbred and they can have physical or mental problems as a result of that. Watch out for that if you make your choice. A dog that is in the top 10 of most popular dogs is not always a good choice, so make sure you know the breeder.
A good breeder will look at your family situation and at your previous experience with dogs and advise accordingly. An older dog can be fine, but again, you have to know its history. There could be hidden issues that you get to deal with later on in its life. Fear, aggressiveness, a lot of it can be solved, but you have to know how to spot it and then act on it.
Having a dog is rewarding and you get a great companion, but it is also hard work. It makes sense to go to a puppy course, not just for the dog, but also for you. You have to know a bit more about dog behaviour if you get one, otherwise there is the danger of the dog going wrong.
Cairns are good with kids, their coat has to be plucked once or twice a year to get rid of the excess hair, they are not overbred and although they are small they are real dogs.
Good luck with this.