A task that could work as a “sharing online safely” activity would be getting students to play a guess who style games about themselves.
Students would write a list of facts about themselves, that would then be shared with the class. The class would then stand up if all the facts read so far were true for them, and sit down as soon as one wasn’t.
This could then be later explicity related to online privacy and safety, by discussing how few questions it took for them to be the only one standing, and thus the obvious person the facts were about, as well as discussing which questions were true for the whole class (e.g. school, age) that might also help them be identified online.