I will also tell you =>Border Terrier (from FIRST HAND EXPERIENCE) around a LOT of them at my local kennel club classes & tracking tests. Even though small, I saw one WILLING & ABLE to go over large, fallen trees, in woods - while getting a TDX. At that point, I said if I eventually HAVE to get a smaller dog, this might just work!
I have sporting dogs - love their willingness to please & versatility and work ethic. BT are one of the few child-friendly, terrier breeds I've found that you can do lots of things WITH, like tracking, agility, as well as fairly competitive obedience, nose work, barn hunts, and rally. Some will even retrieve!! The coat does need to be stripped but (unlike many terriers) is a low, or non-shed type; better for allergies or housecleaning purposes!