postID/postname should work faster.
Had a similar dilema and it turned out WordPress did all the 301 redirects automatically:
Changing pemalink structure to /%post_id%/%postname%/
Didn’t measure any rating or traffic drop. However, in the first week, page load time did increase because of most visits being redirected. After that, all fine.
Make sure to change all the internal links, so they point to the new address, otherwise, users clicking on them will be redirected. Not very bad, but not perfect either.