My idea would be to seal the dirt floor with some plastic and a 2" layer of concrete. Then cut a hole into the basement wall through to the crawl space ...enough to have at least a 3'x3' access. There are companies who cut concrete, it is about $250 in my area for this hole.
This gets you away from having to install vents which do not work in my opinion.
You end up conditioning this small space with basement air..and a dehumidifier.
Also better for your stored belongings to be in a constant temp.
We do this on all our remodels when there is a crawl space..no issues yet.
Good luck with your project.