(Been thinking about Finnish/Finnic mythology a lot lately and they have a yin/yang type division of things into upper and lower that could slot somewhat into your Solar/Lunar system, but that's not why I started to reply to this.)

I don't really know how to live with Beltane's heterosexual imagery but I think I would approach it as, at core, human and animal fertility, so for me with my wife and our baby in our very normative domestic and comfortable life as married queers, it could be giving thanks for our kid and spending time with family, I guess? When you think about Beltane as a festival of sex for fertility--well that's not a giant concern for most people, is it? Most people are not actively trying to get pregnant every single spring. So unless you raise farm animals, you HAVE to conceptualize it differently, if you mean to celebrate it at all.

I've been going over my head how, if you equate the wheel with human pregnancy cycle, conception actually occurs at Imbolc, if the God is to be born on Yule. So Beltane should really be the celebration of entering the second trimester, when the embryo is more likely to survive.

*throws hands up* Idk man.