I played with yuka for a while and I am quite happy about it. Managed to use it to move my aircraft carrier following path and for bird flock I can now chase with my plane. Post with video here
Few comments on yuka:
-I think its not fully 3D as its meant mostly for FPS games. For example wander behavior is only x,y (there are others only 2D). I suppose its fine when combined with follow path. Fortunately its easy to extend.
-I had to add a behavior for limit sphere/box otherwise birds would just wander away.
-Not sure what is the physics aspect doing in there. For birds I added functions to adjust the speed based on up vector so it looks like it speeds up/down on climb/decent.