I can hardly follow the timeline here, but generally speaking, you should give everyone a heads up about what is going on and just let the chips fall where they may.
Just be honest! Just say you feel like you bungled this up and you're not sure what to do. I'd be really weirded out if I had a vacation planned with a smaller group, and a 4th family just showed up without me knowing. Even if they have their own house, if the expectation is you're all hanging out together, then something needs to be said. |
The vaccinated part is the crucial part here |