Hola Emanuel
Yes, it would be correct but the meaning would change:
¿Fuisteis a Ibiza para vuestra luna de miel?Did you go to Ibiza for your honeymoon?
¿Ibais a Ibiza para vuestra luna de miel?
Were you going to Ibiza for your honeymoon?
The preterite is expressing a completed action in the past while the imperfect is expressing an ongoing action "to be doing something in the past", or in this case with verb "ir" it has a specific nuance, as if you were saying "Were you planning to go to Ibiza for your honeymoon?
Saludos
Inma
