Sister`s 18th

My sister is turning 18 in a month and her birthday is on the night of `Jazz night`, (It`s a band concert for Jazz bands and it`s tradition for grade 12`s to go to BP and there`s not enough time to do anything for her b-day). My sister is really mad about it and even claims she wants to skip her birthday. I can`t do anything regarding her b-day at Jazz night for many reasons (It just won`t work). So I though of throughing her a surprise birthday party a week before her actual b-day. But the thing is I don`t know how or what I could do that will really make her 18th a b-day never to forget. Any ideas would help A LOT.