Ask HN: Best mask for wildfire smoke / extreme air pollution, children included?

Wildfire season for California and the US West is drawing near. While I have a pair of effective air purifiers for my home, as well as central AC, I want to be better prepared for unavoidable outings than I was during the Camp Fire last year. I have a 3M P100 ("Dust") mask that I wore outside last year (with replaceable filters), which may have been overkill (though having lived in Beijing previously, I'm inclined to err on the side of caution).

Does anyone have recommendations for less ostentatious (but still effective and certified) masks suitable for wildfire season, or even just high PM2.5 days? Especially for small children? (Have an infant and would like an option just in case an outing is absolutely necessary.) Reusability would be great, if it's possible without compromising effectiveness.