You're welcome Carl! I made them in CAS and they spent every second playing and singing to it, besides the time taken to teach them their skills. So they spent at least 5 days straight singing and playing with it. Then I got the pop-up saying it was going to be their birthdays soon, so I bought 2 cakes and used them. They are now children, but the dolls are still just dolls.
I have the kids playing in the sandbox right now, hoping their dolls will turn soon. Wait, maybe if I take them out of the inventory? I'll be back!
EDIT: After less than 3 minutes on the ground, they turned!!
So I guess it doesn't work in inventory!