hi sgblingff,
it's not up to parents to decide if they need to attend or not. it depends on ur in-law's grandparents whether they're inviting ur parents. usually, formality sake, they will invite the bride's parents with an invitation card.
i'm hakka, customs very similar to cantonese, and my hubby is hokkien. you may refer to my messages posted earlier in this thread..starting frm end-july.