I'm no expert about this topic (effects of society on evolution), but it seems to me like after a certain age, there are diminishing returns from having grandparents. One critical point might be when you get a stable job. After that, the role of grandparents probably can't compete with other selective pressures to keep those grandparents cancer-free. Right?

As to having children later in life, that could certainly help the situation, but only if we all agree to do that. If there is some genetic factor that determines when a person wants to have kids, then people who want to have kids earlier will likely win out.