Bare Minimum Legal Docs Before Open Heart Surgery?

I (65M) am quite unexpectedly having open heart surgery next month. Feel like I am totally healthy, apparently not. I've been told I'm high risk, and it could turn into an emergent transplant.

I have advanced healthcare directives that names my fiancé to make my medical decisions. That is all.

My mom is still alive and I pay for and manage her care. I have an adult son and two grandkids who are fully self-sufficient. I am still working (self-employed). I'll be starting Medicare on January 01. I don't take Social Security yet.

What documents should I prepare to protect my loved ones in the worst event?

And can I do them myself/via Legal Zoom or do I really need a lawyer?

I've looked into a living trust previously, but now I'm wondering if that's too convoluted to set up in this short ~4 week timeframe with everything else going on, including the holidays.

My main priorities:

• Make sure my mom is taken care of, and that I can leave things to my son
• Protect my fiancé. We live together in a rental and I've been told in Idaho there's no law that says our stuff becomes hers. I don't want our belongings to go into probate and her have to deal with that?

Any guidance on who to see or what to fill appreciated.