After bouncing on a trampoline, a mouse is capable of air jumping, even if they jumped onto the trampoline prior.
Trampolines are generally used to bounce to the cheese when it is high over the mouse's head; or over obstacles, such as walls or fans.
To best utilize the trampoline, jump while at the height of your bounce.
When placing a trampoline, note whether you will need to stabilize it. Sloping surfaces, unsteady constructions, loose objects, or wind can all negatively affect the usefulness of a trampoline to your mice. If your trampoline needs securing, any of a number of techniques will suffice.
Placing a trampoline under a crowd of colliding mice is an exercise in futility.