I've done this a few times. It depends on how old the PCs are, in my case they were 10-12 years old. IIRC my last set of rules were
All stats -4 with a min of 6 (based on what they meant to be when they were 1st level)
No classes or proficiency bonuses
Pick 1 skill you're proficient in
Nobody picked classes until they hit first level and the biggest threat they it (other than other kids) was a dog. A big, scary dog. Named Fifi. Before they went to 1st level they were allowed to change their mind of what classes they wanted and what their stats were.
It was mostly RP and introduction to the world/city they were in but it was a blast playing kids.
All stats -4 with a min of 6 (based on what they meant to be when they were 1st level)
No classes or proficiency bonuses
Pick 1 skill you're proficient in
Nobody picked classes until they hit first level and the biggest threat they it (other than other kids) was a dog. A big, scary dog. Named Fifi. Before they went to 1st level they were allowed to change their mind of what classes they wanted and what their stats were.
It was mostly RP and introduction to the world/city they were in but it was a blast playing kids.