It sounds like the 'path of least resistence', however, would advise that (regardless of how small the courses are), restore process had better work ... bringing across all accounts/student work, grades, etc. ... or ?
Normally, I'd recommend installeing a 'sandbox 2.4' on same server, but that might be a little too much.
Sooooo ... one could test restores of courses rather easily (maybe) by installing a laptop version of 2.4 Moodle. Get it running. Then backup your 2.2.x courses, download the backups, and restore to the laptop version of 2.4.
Then you know for sure (or as sure as one could be, I guess)! ;)
'spirit of sharing', Ken