IMHO this can be used more generally - look at pet-projects that people are making in their free time. There is no such thing (in most cases) as deadline or "finish", because there is always something that can be added, improved or taken care in any way. Keeping all ideas in a notebook allows you to review them with other contributors, and even when project would be abandoned, this would allow to refresh memory when someone decides to come back later.

In this case however, having some quality time with son is the most important thing, and putting a deadline would affect the fun for the worst.