I need ideas ladies! the big 16 is coming up! what should i do?

so I'm turning 16 soon and i have no idea what to do to celebrate it. My mom won't let me have a party (we can't afford it and I dont want one either). another thing I have to think about is the fact that my closest friends come from different cliques and I don't want some to be awkward around each other ya know? I was thinking of inviting them to celebrate at a water park or maybe movies and dinner? i honestly have no clue. I dont want people to feel weird around one another cause they don't know each other. But at the same time i want all my close friends there. any ideas on how i should celebrate? I'm desperate for ideas! My birthday is on the 21st and my mom needs to know ahead of time!