Throwing a party, need help?

so at the end of the year im throwing a big party at my house. but it will also be my sisters birthday weekend so it will be incorporated into the party. shes becoming a teenager... already... and i have TONS of little brothers and they all have friends that will be coming so im getting a moon bounce, which most of my friends think will be fun (where upperclassmen.) also im getting a huge wet/dry slide. or a water ballon battle field. were going to set up the volley ball net and our basement will be set up nicely for hang out. what else should there be? im getting speakers to for music. i want this to be super cool.. so help me PLEASE