The SmoothCam node in Shake takes a second matte input where you can define areas for the algorithm to ignore when analyzing your shot's motion. So try making a loose matte around your walking guys, plug it in and see if that improves the result? You might improve Furnace's Steadiness results by enlarging the box used to define the area to perform motion analysis? If i remember right, the defaults center the box in the viewer around 50% of the shot.
There are a few ways to smooth the shot in both Shake and NUKE using 4 pts of tracking data.
One way in Shake: use 2 Stabilize nodes. In the first, track your shot using 4 pts and set inverseTransform to stabilize. In your second node, load the 4 pts of tracking data from the first stabilize node, then smooth the data in the curve editor to your liking. The idea is to first remove the original motion, then re-introduce it using smoothed curves.
In NUKE you could use a tracking node, enable 4 pts, analyze, then under the node's transform tab, set transform knob to remove jitter. You could animate the jitter period knob to smooth the camera move at the tail of your shot.
Or, use a tracking node to find 4 pts of data then load those into the 'from' tab of a CornerPin2D node. Copy and paste all 4 points to the CornerPin2D tab ('to'). At that stage the node doing nothing because you have inverse expressions. But you can then view the 'to' data in curve editor and filter it to smooth your shot. This method is similar to what I suggested using Shake.
Good luck -Ean