Wild guessing: check if there are any USB (boot) options
If the tablets are just booting into Windows I doubt it. I have a vague memory (probably wrong) that you only get multi-boot if in developer mode.
However, as a slightly heretical thought, if the Windows tablets are running OK under Windows can you not simply install Kodi on one of them. Not as good as running under LibreElec but might give you what you want.