Buddhism emphasizes compassion, kindness and bodhisattva's heart. As long as you have a good heart, your behavior is good. If the birthday for the elderly is for the purpose of respecting and honoring the elderly, then it is human nature. However, traditional birthday celebrations can also lead to killing, which needs to be grasped. It is immoral to hurt other beings in order to do a good deed. Therefore, many Buddhists would rather not do it in order to avoid killing. If the relatives and friends at the banquet are in favor of vegetarianism, you can have the best of both worlds; You can also use western etiquette forms such as cakes and candles that don't kill animals.