As plurals of elf, both elfs and elves have long histories in English, and there is plenty of precedent for both, but elves has always been the more common form by far.
This issue around wrongly placed apostrophes seems to have escalated recently. It would appear to be almost a badge of honour to place as many apostrophes as possible on signs etc. It would be better to omit them altogether rather than place them wrongly. Love the 'elf's and shelf's '