Go to a hot air balloon festival. -> Been there, done that. I actually went to one of those festivals with my parents and brothers when I was a little kid. We didn't go on a ride, but it was awesome anyways =)
Love lock bridge in Paris. The idea is, couples go to the bridge Passerelle des Arts in Paris. They write their names on a padlock and attach it to the bridges railing and then throw away the key in the Seine river to symbolize their undying love.