Things do change wannabe so don't give up. I do think its the choice of your son and his wife, you should not tell them how you feel. Can you do some voluntary work with children e.g. helping with reading or supporting a child with disabilities. There are so many people you could help, grandchildren are not the be all and end all of life. I know this is GN but there are others on here who are not grandparents.
Humza Yusaf's resignation speech
Air fryer - combi microwave - oven? Help!