io_uring supports submitting openat requests, which sounds like what you want. Open the dirfd, extract all the names via readdir and then submit openat SQEs all at once. Admittedly I have not used the io uring api myself so I can't speak to edge cases in doing so, but it's "on the happy path" as it were.
https://man7.org/linux/man-pages/man3/io_uring_prep_open.3.h...
https://man7.org/linux/man-pages/man2/readdir.2.html
Note that the prep open man page is a (3) page. You could of course construct the SQEs yourself.