What is proper etiquette for gift giving for renewing wedding vows? I've been invited

A co-worker has invited me to her renewal of wedding vows. What is the proper etiquette in this matter? Do I give a gift or not? What is the proper attire? She is wearing a hawaiin dress that ties like a halter at the neck and some flowers around her head and ankle. Her husband is going to wear a lei. I've never been invited to one of these so I'm uncertain of the proper etiquette(s). The ceremony will be held in her home with approx. 50-75 guests.

WELL EVERYONE IVE WENT TOO ;WAS A GIFT ? KNOW CHECK OUT MISS MANNERS ON THE WEB ......YOU JUST MIGHT FIND YOUR ANSWER:) I THINK ITS OK BUT NOT A RULE CAUSE I JUST WENT TO A INGAGEMENT LUNCH AND I CHECKED MISS MANNERS AND IT SAID IF YOUR CLOSE FAMILY MEMBER OR JUST WANT TO GIVE ITS NOT TO BE EXSPECTED..... (from the couple) HOPE THAT HELPS:)

Any time I have been invited to a renewal it has always been indicated on the invitation "best wishes only". I don't know if that means that my friends thought that gift would be expected otherwise? or they didn't know the etiquette either, so thought they would save some the embarassment

One of the gifts I got that I thought was wonderful when I got married were tickets to a local production of a play. It was a very fun night out, and within the budget ot the giver - just a thought if you do need to have a gift - maybe a gift certificate to a polynesian resturaunt (in keeping with the theme) if there is one around you?