Which law supports why trampolines are good toys for kids that like to jump high?

Jumping on a trampoline is an excellent way to illustrate all three of Newton's Laws. Trampoline shows Newton's three laws as the following:

The first law, which tell us that an object will continue moving unless acted upon by an outside force, is illustrated by the fact that you don't soar into the sky when you jump up and that you don't fly through the bottom of the trampoline when you come down. Gravity and the springs of the trampoline keep you bouncing.

The second law illustrates how velocity changes with the equation F=ma, or force equals mass multiplied by acceleration. This simple equation is used to find the equations for kinetic energy, where acceleration is simply gravity. This means you (the mass) multiplied by the acceleration (gravity) equals the force upon the trampoline.

The third law says that every action has an equal and opposite reaction. This is illustrated by Hooke's Law. When the springs are stretched they exhibit an equal and opposite force, compressing back into equilibrium and propelling you up in the air.