Published or not, "happiness research" is notoriously difficult. It isn't exactly hard science.

Here's another personal opinion: our daughter is pretty much the most important thing I've ever done, and even if something like Hecl were to become hugely popular, she still would be to me, although perhaps not to the world at large. I would bet that someone like Linus might feel similarly.

Many other things you do in life might have significant impacts on lots of other people (perhaps adding up to 'more overall impact'), but a child's life and future is entirely in your hands, which is a huge responsibility.