Posting here because I'm not entirely sure anyone uses the Gameplay Mods section. I've created a mod that does what the "setage" cheat can't: Set sims to any age, including neighbors.
I've had it come up quite a bit in my cheat thread and I had to shoot down users who were asking because the setage cheat only works for setting to adult due to a bug in the game's code.
This mod adds in tm.setage which is a custom cheat expanding and fixing this command.
http://forums.thesims.com/en_US/discussion/787109/release-set-age-cheat-set-your-sims-and-neighbors-to-any-age
Comments
1. Check the script mods box in Options > Game Options > Other > Script Mods
and
2. Right-click the game in origin and check for updates.