Is there a way to filter out all of the bad language and age-inappropriate videos on YouTube for my kids?
There's no way to filter out all of the bad language, age-inappropriate videos, or negative user comments on YouTube. Google, YouTube's parent company, has a guiding philosophy of an open web, where pretty much anything is allowable -- unless it's illegal, harmful, or extremely offensive. You can always opt to use other, more tightly curated video apps (including YouTube Kids or any of these) instead of the almost-anything-goes YouTube site. But if you or your kids want to stick with YouTube, try these built-in features to make it a little safer for kids.
Subscribe to channels you like. Subscribing to your favorite channels adds them to your feed, so kids can easily click on them when they log in. Subscribing also helps YouTube determine other, similar videos you might like.
Enable Restricted Mode. In your YouTube account settings (the little gear symbol), turn on Restricted Mode at the very bottom of the page. That should cut down on some of the age-inappropriate stuff.
Turn off Autoplay. The related videos next to the main video you're watching will play automatically unless you toggle off Autoplay. Turning this off prevents a potentially age-inappropriate video from playing.
Use a video blocker. Downloadable video blockers are created by third parties. You can add them to your browser and configure them to block videos by channel, subject matter, or keywords.
Keep kids on kids' videos. This is a little bit tricky, but videos designated for kids don't allow comments. If you see comments on a video, it's intended for viewers 13 and older. There should be a big white space (and perhaps an ad for the YouTube Kids app, instead of the usual comments.