If your mom knows how to do ballroom dancing, you can do it with a group. I know a lot of people of this age go to dance halls or big squares to dance. It's easy to get to know a lot of dance partners.
If you have a sports background and money to spare, you can take up yoga, aerobics or swimming.
And you can climb Baiyun Mountain or go to the park. There are a lot of people who are interested in getting together and singing together.
And you can participate in the Guangzhou Volunteer Oh, you can help more people in need of help.
There's also the fact that if your mom doesn't mind working hard, you can do part-time work to help people with their health.
At 40 years old, you may not be interested in singing Cantonese opera, but you can sing more revolutionary songs in your own time.