My Dad Is Going To Get Me A Dog For My Birthday. What Kind Should I Get?

Don’t worry, we’ll either be getting it from www.petfinder.com or a breed rescue. I already have a German Shepherd & a Greyhound at my mom’s…I want something that is/are:
-Protective of me
-Very loyal
-Medium in size(not over 80 pounds)
-Easily trained, obedient
-Short to medium length coat
-Likes to go for long walks
-Good with little kids
-Reserved. Isn’t overly friendly when meeting new people.
No “designer” mixes,please. I’d like a breed or mix that I’ve never owned before so please no Greyhounds or Shepherds. I will be taking sole responsibility of this dog/puppy.
Thanks!!(: