Howdy! Instead of tagging as a park, have you considered tagging Little Sahara boundary as a protected area? [1] Even though (imo) neither park nor protected area is perfect, I understand park to mean more of a developed green space that's more managed. [2]
Also, for the dune outlines themselves, please consider avoiding descriptive names. [3]

Let me know what you think! Hope it doesn't seem like I'm trying to boss you around. Thanks for your import of this boundary, and your other contributions!

[1] https://wiki.openstreetmap.org/wiki/Tag:boundary%3Dprotected_area
[2] https://wiki.openstreetmap.org/wiki/Tag:leisure%3Dpark
[3] https://wiki.openstreetmap.org/wiki/Names#Names_are_not_for_descriptions