Hi
I had my jack russell from a pup, she is the best little dog i have ever had. You said you were gettng one from the rescue centre, I think it would be nice to have a rescue dog, but for children I would suggest a puppy, as they learn to grow with you , they are very intelligent little dogs. very loyal to there owners. Some JR can be a bit unpredictable so would be bit weary of an older dog. But you have picked the right choice. My JR loves children. As long as you pick one thats good with children you should be ok.