What can you tell me about the Imagination cruise(or any cruise)(really long, please help)?

I have almost a 100% chance of going on the Imagination cruise in the summer(september I think).(the reason I say almost is it was a 50/50, and then one of the people they were going to take(their foster kid, just moved out, so if he still goes with them then I can't but if he doesn't than I will). I am a 15 year old girl and have never been on a cruise before. Since I am only 15, do I need a passport or just my birth certificate. Also can 15 year olds go to the casino on the ship? I heard they can drink alcohol(not that I drink) but what else can they do. I am assuming they are not "adult" enough to go to the "Serenity Adult-Only Retreat". Is the age for that 18?. What are some things that teenagers need to pack. I went to some websites that said passports, money for tipping, etc. but I don't need that stuff, do I? I am nervous about going. I heard that there are teen parties and stuff, but I have a boyfriend, and he asked me not to party and drink while on the cruise. I don't just want to go back to my room at night, but I don't know. maybe I can just party with the girls. I also have this engagement ring(my sister gave it to me after her and her fiance broke up), and I was going to wear that when we went to the teen parties just so no guys hit on me. I am so nervous. I feel like I am forgetting something. I know you have to bring a really nice outfit(my mom is supposed to take me to the mall and get me an on sale prom dress). I have a nice homecoming style dress(strappless comes above the knees, never been worn except to try it on) should I bring that as well? I know shorts and tank tops, but do I want casual or more dressy stuff? anything else you guys can think of? I will probably post additional details, when my brain calms down and I can think better. I have known for a while that it's a possibility of me going, but now that their foster son left, (he's 18) I think I have a higher chance of going.