Is it proper to give gifts to people who help at Birthdays?

by Victoria
(Fremont, CA, USA)

My sisters and I gave my mother a 75th surprise birthday party. In the invitation we asked that in lieu of gifts, please share a photo or endearing story about our mother to be put in a keepsake book. Some people offered to help in anyway since they were not giving a gift. One niece handed out the Trivia game sheets, another handed out pens for the games. They also helped pour the apple cider. I feel that their helping was their gift of love to their grandmother since they did not give her a gift. My sister on the other hand felt that we should give them a gift card or gift to thank them for their help. Is their any etiquette on giving gifts to people who offered their help at a party. I feel that giving them a gift for their gift of love to my mother would maybe make them feel uneasy.
Please let me know if this is proper to give gift cards to people who want to help when are told not to give gifts to the birthday person.
Thank you for your response.