I don't think this is a sound plan. A lot of young families rely on grandparents for childcare, but if grandparents are all working, the government will have to pay for more child care or people will exit the workforce to raise their families and therefore not be contributing to the economy.
Additionally, there are so many jobs that would be impossible to perform well in later in life for the majority of employees (no, not all) but employers would face discrimination charges if they sacked their 70 year olds on age related grounds. But if working until 70, i imagine a lot of builders would be a bit slower going up and down the scaffolding or couldn't carry as many bricks up ladders. I imagine insurance policies would also increase, buildings would take longer to be built and costs would go up even more. Prisons would be full of riots as the septuagenarian staff are over powered by the inmates. Editors wouldn't be able to read as they would be awaiting cataract surgery. And those surgeons would have shaky hands. Teachers would not be able to carry all their marking home let alone have the energy to mark it. Speech and language therapists would be too hard of hearing to hear their patients. Waiters and waitresses and shop workers and factory staff and people working in museums, libraries, cinemas, galleries wouldn't have the energy to be on their feet all day!