feel my situation is very similar to yours. The first time I met my parents-in-law was because they were sick, so I went to see them. I think since you are visiting a patient and it is the first time you meet them, I think you can buy some more expensive nutritional supplements.
Generally, you bring fruits when you visit a patient, but since this is your first time meeting your parents-in-law, you cannot appear petty, nor can you treat them as ordinary people. More expensive nutritional supplements, firstly, will make them feel that you are caring and hope they are healthy, and secondly, they will feel that you value them and do not treat them as ordinary people, which is very commendable.
In addition to nutritional supplements, you can also give some health care equipment as a gift. For example, if your father-in-law has high blood pressure, you can give him a blood pressure monitor, a blood glucose meter, or a small massager, a foot bath, etc., all of which are fine.