How to animate a large number of interlocking objects?

I want to build something like a busy warehouse where people are moving objects to and from carts that move around to other destinations, but I don't know if I should make a group with all the moving parts and put the humanoid and other parts in that model and see what happens, do I tween all parts by hand (which is the most likely to break because of lag), or do I do a hybrid approach where I script animations and tweens to get the desired effect.