Commitment ceremony is similar as wedding ceremony that binds two people together. But it is usually for a gay couple which is not legally binding. The two agree to share each others life in the front of families and friends. When you invited to a commitment ceremony, you should keep in mind the couples tastes and other aspects then prepare the gifts as the traditional wedding.
Like any getting married couple, the two persons will start their life together. Some practical items ca not go wrong with your gifts. Such as bedding, linens, china etc. To make it specially, you can consider the couple their tastes. If they love pampering themselves, you can give them plush, matching robes and slippers. And if they enjoy entertaining, a great bar set; complete with martini glasses and shaker would be thoughtful gifts. Someone who likes reading, the best-selling books together with a reading lamp would suitable.
If the couple interest with art and history, a museum family membership is really special and thoughtful. They can visit the art or history museum unlimited times, at the same time they can get some discount of exhibitions and other supplied items.
If you want to give a nontraditional gift for the couple in commitment ceremony, you can choose to donate to a charity in the name of the couple. But you should aware of charity meaning you select. For example, you can make a donation to a charity that campaign for gay rights such as the Human Lesbian Task Force, National Gay or Rights Campaign. Although it is not an actual gift, they will surely appreciate the gesture.