Moving out of state after only 2 months - need advice on when/how to give notice

I’m looking for some advice on giving notice to two NFs.

I started nannying for two families about 2 months ago (one is 4 days/week and the other is 1 day/week). Both have been great fits so far, I get along well with the parents, and I enjoy caring for the NKs.

The issue is that I’m moving out of state in about 7 weeks to help care for my grandmother. This was unexpected to be needed so soon, and I had no plans to move when I accepted either position. I normally stay with families for at least a year, and both of my previous nanny positions ended because the families could no longer afford to keep me, so I’m feeling uncertain about leaving these families so soon.

I want to handle this as professionally and respectfully as possible. I’m planning to give at least 3 weeks notice, but I’m struggling with when to tell them.

My concern is that if I give notice 5–6 weeks ahead, they could potentially find a replacement and end my employment earlier than my planned move, leaving me without income for those remaining weeks. At the same time, I don’t want to give them too little notice or make their childcare situation unnecessarily difficult. I’m also not quite sure how to word it when I do tell them. Should I tell them in person or in text over the weekend? Should I give a lot of details or just the bare minimum?