According to Wikipedia co-housing is:
a type of intentional community composed of private homes supplemented by shared facilities.
These shared facilities could include anything like communal gardens, kitchens, child care and so on.
Co-housing differs from many other collective living arrangements in that they maintain a significant degree of privacy. Only the shared facilities are managed collectively.
Because each family has its own private place, co-housing might be attractive to a wide range of people. And different program could have different collective arrangements, people could choose the project which suits their preferences best.
In his book Sex in the Future, Robin Baker argues that single-parent families will become the norm in the near future. Baker also suggest that two or more single parents might opt to share to live together. This because single parents could share their costs this way.
Co-housing is interesting for single-parent families especially when such arrangements include child care facilities.
There is nu reason why co-housing could not be integrated within the concept of garden cities. With a little adjustment the garden city design could include co-housing. This combination would enhance social cohesion.