@Teaceratops I made some similar plan for this to go back to New Zealand at some point in my life without flying
You can go from Paris to Moscow in train, then to Vladivostok, east Russia in a week of train with the trans Siberian railway
From there, you can reach japan with a boat line
The main issue with this part is that I don't think I'd be safe in Russia currently, but it may differ for your family.
I didn't look past that point, since I got basic sailing training that could help me get on a crew so sails around the ocean
I have heard it should be possible but uncomfortable, and possibly quite expensive to get on cargo boat. I never checked in details, but their should be lots of traffic across this part of the world
I would double check with your embassy on the path to avoid dangerous place/pirate and see if they have advice for you