Looking to move to an A7iii - have some questions.

[P1505]

Hi all.

I'm hoping you can help. After many years of shooting with my trusty Leica M9 (which I still have and shoot with daily) my eyes are starting to change and I'm looking to move to a camera system that has good autofocus. After 20 years of contact lenses and a never changing prescription, they've suddenly started getting "better" and for the years this will happen manually focussing is... yeah! Tricky.

I shoot all sorts of stuff, a lot of candid/street type images but mainly a huge amount of my family. A six year old and a 3 month old. I've been shooting hyperlocal for a while to avoid having to focus, but I like a shallow DOF and wide open I miss things now that I used to get.

I did have a Leica Q but the battery life was terrible and the auto focus wasn't great to be fair, slower than me manually focussing. Amazing images though. I tried a Fuji X100F (or T, can't remember) and that was fun (I have the original X100 which I keep for sentimental reasons) but the manual focus was slow and the autofocus wasn't worth having. And again, you had to walk about with 5 batteries in your pocket (I charge the M9 yearly whether it needs it or not).

I was thinking the A7 iii may be the way to go. I can focus peak with manual lenses, I can stick a 50mm or 35mm autofocus on it (I like primes, when I have a zoom fitted I use the two extremes and nothing in between, I don't know why). What I want to know is how good is the autofocus really? I never shoot video, everything I've found is all about the autofocus for vloggers. I want to know about still shooting. What lenses will I need to invest in to get that Canon or Nikon level speed without having the massive body? What is the battery life like in real life? Will I be walking about with a bag of batteries?

In reality to get the speed of autofocus I want (hard to define via  forum but imagine a 6 year old doing his thing and I need it to track him as he runs about with the lens wide open) am I fooling myself, and should I invest in a DSLR or buy an old Lytro camera and change the DOF later ;)

Any advice appreciated. Ready to buy immediately. And cry later about the cost!