The way it was originally set up here, a Master Mason had to be present for them to start their meetings. I don't know if that's any longer the case. But in the US, it was organized and created by US Masons for Masons and their wives, so there has never been anything shady about it.
Well, I know, that it is a perfectly normal part of the masonic environment in the USA and in some other countries as well. But, especially the crossover does seem problematic for me. Not that a freemason must be present, but that he ist present
as a freemason.
Every brother can be part of non-masonic organizations, chivalric orders, brotherhoods, social clubs, and, and, and. But he is always part as a member of that organization. Even if that org. requires him of being a mason, like the Shrine, Tall Cedars, or masonic groups, that can not confer degrees, all members are there, just because they are members, not "as masons".
I'm not sure, if I can express the difference, I want to point out here. Put it on my account, that English is a foreign language to me.
If the OES would be a "mixed-gender organization for masons and their wifes", and otherwise has nothing to do with the lodge, I would abstain from it by personal taste (no interest, lodge as it is, is enough for me), but would have less problems with its status.