Boxer.
Check out one of the boxer rescue places and you could get an older rescue dog that will be very mello. When they are young they are little crack heads but once they hit about two they mello out nicely.
I have always had dogs, muts, labs, goldens and such, but my police officer buddy rescued an abused boxer from some inner city thug that he took to jail, and he has been the best dog I have ever had. I think the rescue dgs really understand what you have done for them.
Anyway, boxers are very loyal, and extremely well tempered especially with children. My two little ones can climb all over him and he does not blink an eye. I was kind of worried bringing a 50lb+ dog around my little ones but once I started researching I fealt a bit better, and now after two years with him I completely trust him. They are great. I am a boxer man for life, I will definitely have another later on.