Well you obviously seem like a genuine nice guy, and i really dont think this girl deserves you to get her such an extravagent gift such as the balloon ride as you are no longer together and not obliged to each other. Think...would she give u the same gift? I know that isnt really the point, but you dont want to look like your still 'out' there just for her, hanging round for her, waiting for her to come back, whether you are or not, and a gift such as that will only make her think this.
Get her a simple, friendly card, and a present like a CD, DVD or something, but nothing too personal or intimate, and congratulations for being so level heading and not holding anything against her...you are quite a rare person for not being bitter etc
******* 7 Times World Champion Michael Schumacher - the ultimate sporting hero *******