What to do for my brithday?

My 18th birthday is coming up and idk what to do. I want it to be significant because I'm turning 18, but it can't be anything you need to be 18 for because only two of my friends are older than me and will be 18 already. Over the years I've done bowling, ice skating, movie night, overnight condo by the beach, magic mountain (it RAINED), stuff like that. And my cousin just had her 18th and she did laser tag. My other friends birthday is right before mine so I'll have to wait to see what she does. So, I'm out of ideas. I don't want it to be something ourdoorsy because it ALWAY STINKIN RAINS ON MY BDAY. It's in March so beginning of spring and it rains almost every year. So something inside. I'm a girl btw if that helps. So there's like probably 4 people besides myself that would go. And possibly my brother and cousins who are guys unless it's something girly. I can't think of anything I or my friends haven't done yet that's not too horribly expensive. So, any ideas? My mom keeps asking what I want to do!