DMU Kinematics is pretty cool to animate mechanisms, but it has several limititations: it only handles closed loop, single-solution mechanisms containing only rigid bodies.

To simulate the button motion, you must create two mechanisms: one before the button makes contact, and one after the contact is made which moves the other parts. You might be able to simulate both mechanisms by using laws to combine both mechanisms and establish some time parameters for when the first mechanism moves and then when the second one.

Springs are not rigid bodies, so the spring motion can not be simulated. (you can fake it by breaking the spring into two halves and adding a prismatic joint between them)

You might want to check out the DMU Fitting Simulation workbench if you want to animate moving parts with collision detection. Or check out some other software that does dynamic analysis (such as LMS Virtual Lab that can be added as a CATIA workbench)