I gotta go with SFChuck on this. If the music is so loud that it competes with the voices, then even filtering "background noise" and using similiar options that Audition and SoundPro, etc. might offer, will be useless.
Whenever interviewing people in noisy situations, loud music, etc., I use a lav mic and try to separate the subject as much as possible from the source of the interfering noise. A lav will tend to accentuate the closest sound source and lessen other noise, which is why I always tell budding wedding videographers not to make it a "shotgun wedding", but to use lavs.
If possible, go back to the people with a portable DVD player and video of what you've got so far. Have them voice-over what they said while watching their lips on the player. You can then add a music track with lowered audio to simulate the conditions at the original shoot.