ever heard of scrambled eggs? one kid sits in the middle and holds their legs tight so they are round like an egg, and the others jump around the person. if the egg "breaks" then it's someone elses turn. the egg's job is to keep the egg shape, if they let go with their arms or their legs then they broke the egg shape and lost.
we also used to sign made up rhymes and double bounce each other. you know what double bouncing is right? when you catch someone elses bounce at just the right time so that it sends you super high compared to normal.
we also played a game called leech, which i don't think anyone but a rambunctious boy would want to play, as it can hurt and is dangerous lol! one kid, the leech crouches in the middle and the other kids run around and bounce around the edges of the trampoline around him, and the leech tries to grab hold of their feet and make them fall.
anyways that's all i can think of at the moment. maybe just play some music while you bounce
add: can also play bacon, one person lies flat on their back and you got to try to flip them onto their stomach. and the bacon can't break form.