You and your wife have never wanted children in your lives, and you are also trying to improve your quality and quality of life.
Couples have more freedom, which is a good thing. Parents are too old and conservative to listen to advice, so why listen to them.
Parents can force your wife to have kids, can't you force your parents to let them mind their own business and enjoy their own happiness.
First, find something for your parents to do, so that they don't have to be idle, or else they will be thinking nonsense.
Second, block their mouths, buy some delicious food and send it over often. Tell them they can enjoy a happy life without children. With kids, all that is gone.
Third, often suggest that they look at other parents, do not have to bring children, live more comfortable, go out to travel, dancing, playing cards and chatting together. With kids, it's all gone.
Whether it's passive resistance or active opposition, you have plenty of ways. What are you afraid of