Since he is engaged in education, I think you can cater to his preferences and give him gifts related to his daily work, such as a pair of pens. Because this year is the Year of the Dragon and it is also a wedding day, you can spend some time to buy him a pair of red pens with dragon and wind patterns on them. First, they are closely related to work, and second, they imply auspiciousness, prosperity, and flying together. Such a gift is simple but not out of the ordinary, so I think it is the most appropriate gift to give to teachers.
You can also give a pair of cups. The cups represent the meaning of a lifetime, wishing the other party a lifetime of harmony and beauty. Although the cups are very cheap, as long as it is your sincere blessing, the price of the things does not need to be considered. I believe that the recipient will not care. On a happy day, what everyone values most is the blessing, not how much money you give. As long as you do it with your heart, your friends will be satisfied. I hope the answer will help you.