Hi,
love this project.
can we have an option to set safe search option for kids if its 
possible? i have local newleaf instance running.
is this something possible, or can be considered in future?
thanks

Good idea.

Looks like it can be done by adding f2=8000000 to the PREF cookie (which 
is a query string formatting key/value cookie).

Though note that YouTube's safe search is famously inaccurate. It will 
not block many things that a parent would likely identify as problematic. 
YouTube Kids is better but still not fantastic.

For now, I would suggest using YouTube Kids, limiting the young ones to a 
set of channels that you have approved, or finding an off-internet 
activity they enjoy like a physical game.

I expect you can find more suggestions on a parenting forum.