Form a Joint Labor Management Committee and conduct a worker survey to assess the need
See sample survey

Bargain for employer to pay for a child care expert to do a report on the feasibility of various options (on-site, near-site, slots in other centers, subsidies, etc.) based on the results of the surveys and the local conditions, and report back to Joint Labor Management Committee.

Bargain for one or two of the options found to be most needed such as child care subsidies for slots in nearby child care centers or funds for after school programs. Negotiate one or two provisions the first time, and then add more in future contracts.