What calligraphy works are good for Buddhist elderly people to celebrate their birthdays? I can only write in lowercase letters. 70th birthday

Many people have written the Heart Sutra or Diamond Sutra since the Tang Dynasty. There is even a saying in history that a person who copies ten Diamond Sutra has boundless merits. However, there are many words in the Diamond Sutra, which can't be completed in March or May. So I suggest you copy the Heart Sutra. There are many people who copy, and there are patterns to learn. Baidu searches for celebrities to copy the heart sutra, which is amazing.