As a Jack Russell owner, I have to warn you that they might not be the best choice for a first dog for you - They are very intelligent, high-strung & stubborn. They can also be very dominating & protective dogs, even tho they are small. They tend to pick one member of the family & stick by them. They are also easily trained, loads of fun & loyal as the day is long. You really have to work hard with JR's - I love our Cosmo like crazy - but she is HIGH maintenance. Even with obediance training & lots of socialization since she was a wee pup, she hates "strangers" (anyone non-family) coming to the house - anything that moves is fair game, including dust mops, vacuums etc....If you choose a JR - do alot of research first & be prepared to be woken at 4 am by a playful pooch. We wound up getting Newman, to help Cosmo slow down a bit.
I will put in a plug for Boston Terriers - Newman is a BT - he's 15 pounds, thinks he's big - keeps right up with our JR. His main mission in life is to love & entertain people - anybody (definatly NOT watch dog material) They have short hair, which is easy to manage. Even tho they're small, they are quite the manly little dogs, having the bulldog type face & the mini boxer type body - strutting like junkyard dogs - Downside - not the most intelligent breed & training can be harder because of that.
Hope you find the right dog for your family! We love our babies & they are like members of our family - they have brought so much love, comfort & fun to us. I can't imagine being without them....