It it wrong to re-do a wedding if......?

My boyfriend's sister and her husband had only been dating eight months when they got married. She was 17. They got married in a living room with 5 or 10 people in attendance. I don't remember exactly why they did it like that, but they did. Now, they're having an actual wedding so that all the family can come and they can have an actual ceremony. Kind of like renewing vows. I like the idea. Go for it!