Vaulty is a good app for protecting your privacy. Hiding things there are easy to do. My issue with this app is that kids can store photos and videos away from their parents. What is your children hiding from you if they are using this app? Not sure if I would be comfortable having my daughter having this app installed in her phone.
Houseparty is a video chatting app that a lot of young teens use these days. It is a good group video for adults, I would say. For children — No. My issue with this app is that it doesn’t require kids to verify their age, it can be used for sexting and cyberbullying. Even if their private chats are locked, risk for sexual content and privacy issues can be significant.
Kik: Any app that allows teens to create anonymous accounts and/or does not require minors to verify their age makes me unease. In addition, Kik comes with web camera capabilities which can be bad when used by 15 year olds under supervision. The app comes with many other functions like a built in web browser and game capabilities.