Is it Children's or Childrens' obsessive online activities

I have an ‘s/s’ question. I’m not sure what it should be.
Is it Children’s or Childrens’ obsessive online activities?

I look forward to your feedback

The general rule is to add an 's.

So, the “children’s obsessive” as the correct possessive.

There’s a bit of an exception if there are multiple instantiations.

For example, if there are multiple teams in a sports playoff tournament, it’s correct to state the teams’ chances, as you are talking about the chances for multiple teams, rather than for a single team.

But in this case “children” is already a plural of the singular “child”, so you don’t need an s to make it a plural, you only need an 's to make it possessive.

(Just to clarify.)

Since ‘‘Children’’ is already plural, your first example is correct.

ETA: I see **gracer **has beat me to it.