I'm in the same ballpark you're in right now. My friend and I are getting a bunch of glow sticks for everyone so when it get's dark outside we have some source of light, so it's like a glow n' the dark party. Did you consider water balloons? If you don't have one, you could maybe consider getting an inexpensive slip n' slide those are always a hit!
im planning on having a bonfire in the next few weeks or so the people who are coming are guys and girls 15-17 years old and theirs gonna be around 70 people coming i don't want to have a bonfire and have everyone say it was boring bla bla bla i have a volleyball net trampoline woods behind my backyard and obv the bonfire im gonna have music and food there too but ya know i just dont want it to be boring i want it to be like a night they wont remember if you could help me out thank you!