I think it was said before, that Pugs are the sturdier of the toy breeds, and I have had several that were excellent with my children. I also want to state that they are IME harder to potty train, and harder to train in general. Very independent, and stubborn little souls. So if you are looking for a breed that is "easy" to train, I would take that into consideration. (Not saying just my experience, but others have voiced it in the past)
I don't know much about Terriers except what I have heard, but correct me if I'm wrong-don't they need an experienced owner regarding their activity level...exercise...chewing...etc?
As far as age goes, you could have a small breed that "typically" lives for 10-12 years (or whatever) that may die at the age of 2 because it got injured in play, contracted a disease, etc. I have lost a few Pugs due to tragic experiences-some having to do with bad (byb) breeding-before I knew better. I now have a Doberman pup that I researched and researched for a reputable breeder. I also have 3 kids under 6-because of his breeding and temperment I am very comfortable with Max and our boys together. I know his lifespan is only around 9 to 10 years, but I'm going to love him for as long as he's here, and not think about 10 years down the road. If that was the case, all the giant breeds wouldn't have homes because everybody would be afraid of that time coming sooner. I do understand not wanting to face that time, but it will come sooner or later, whether you choose Chi, or Great Dane.
Good luck in your search, I'm glad to see you are doing research before you make your decision. I too have made bad decisions in the past, but have learned and moved past that.
Dawn