Genneraly kittens should have food left out as much as they want. Once they hit a year or so start regulating it a bit more. Mom will wean them when she's ready.
It's not really up to me.Let them stay with mom for at least 12 weeks if you can. They need more time with her before re-homing. Best to adopt out in pairs if possible so they have each other to play with — less scary and easier for the humans too.
Are you not able to keep mom’s favorite kitten or two?