Alright, start with another clean game folder (no need to download the world right now) and copy the Library file corresponding to the sims you created into the clean folder. If you don't know which one it is, check the last modified date; it will correspond to when you exited CAS after creating them.
Start a new game in Sunset Valley and try to place the family. If it works, even temporarily, you can save the individual sims in CAS and then see if you can fix them. Without mods, the approach would be to open the cheats console (crtl-shift-C) and enter "testingcheatsenabled true" without quotes, then shift-click on each sim and select Edit in Create a Sim. Instead of editing, just click on the three dots along the bottom of the sim's portrait, then hit the folder icon to save. Repeat this for each sim, and they'll all be saved separately for you to work on later. You can load them by clicking on the silhouettes to the left of a sim's portrait, then selecting the one you want. The files for these sims land in SavedSims inside your game folder, and these files can be transferred from one game folder to another.
When you are working on them, I'd suspect a bad cc item first. The clean game folder won't have that cc, so hopefully you'll be able to load them long enough to remove it in CAS. If you can't though, I don't know what else you can try. Maybe someone else here will have suggestions.