EDIT: I also want to move my families and houses to Riverview from Sunset Valley anyway because there's a lot more space there. So knowing if transferring families is safe would be helpful.
Transferring famblies across neighborhoods is safe, with a few caveats: Relationships outside of the transferred household will be lost. The Twallanian Porter Device supposedly can allow you to mass-move extended famblies across different households, but as this is not an AwesomeWare product, we can't provide support for it, as I have no idea how or if it works.Thanks for your help. =] And I hadn't heard of the Twallan Porter device, so I tried it out and it's saved me a lot of time in transferring my families so they don't lose the relationships. Perfect. And now I know I can safely uninstall the awesomemod whenever I need to, then I guess that's a bonus for keeping it.