changing my kids names on all my old posts?

I’ve tried searching the plugin directory and this forum but not even sure what search terms to use. I need something that will go through all my archives and change certain specified words. I need to make pseudonyms for myself and my kids and if there’s a way to do this without going through each post . . .

Is there something like this already? It doesn’t seem like it would be a big deal, maybe something similar to the plugin I used (I don’t even remember what it was) to import all my blogger photos to wordpress, which changed the URLS and everything. But I have no idea how to do it.

Thanks in advance for any ideas you have!