You can give his father a better men's agate bracelet or an anti-fatigue bracelet. As he gets older, his body is not as good as before, so giving him an anti-fatigue bracelet can effectively solve physical fatigue and make his father more relaxed. If you can't make up your mind, you can discuss it with your boyfriend. After all, he knows his father better and can learn a lot about his family's hobbies from him.
His father will definitely be very happy if he gives him a gift with collection value, such as a customized silver Maitreya Buddha, or silver bowls and chopsticks, purple sand paintings, etc., which are gifts that make people happy when they see them. There is still room for appreciation in the future. Giving clothes and casual shoes are good. Giving health gifts is still more face-saving and they also like it, such as cervical pillows, lumbar massage chairs, foot massagers, etc., which are good gifts for health.
Giving a customized birthday cake is also good, but you must let the elderly see your intentions and your heart. When you go, you should also take the initiative to help with housework, so that his father can see that you are a diligent and sensible child.