Ignore the people who say you need to bathe every day, that's nonsense. If you want to, fine, but it's fine not to also!
Twice a week is fine IMO.
I totally get where you're coming from about feeling tired and overwhelmed. Lots of stuff in my home would get the judgy-pants on this thread well-and-truly hoiked. But fuck-em if they want to judge, I am doing the best I can, and my DC are thriving, even if the house isn't up to scratch.
I do OK with baths though, they get 3 or 4 a week, but often because it's the one place they stop arguing - with me or each other - for at least 10 minutes!
They go in together, I expect yours do too? If not, that's a great way to save time and hopefully they'll enjoy it.
Not having people over when the DC need a bath, seems like a great shame. Good relationships with family and friends are what makes the world go round IMO, what a shame to prioritise a bath over people. There must be a way to do both!
If I had people over when the DC needed a bath, I would carry on anyway, and give them a bath with the visitors there. Why don't you make Wednesday night bath night, come what may, even if visitors are there? They can stay and chat while you bathe the DC, or leave at that point, whichever they like.
Also, what are your relatives like? When my DSIS or MIL come over, they love giving the DC a bath. (The rest of the family, not so much). Would any of yours actually like to give the DC their bath? If so they could bathe the DC, giving you time to catch a few minutes to do something else.