Reuse an alias email address for a new icloud account?

In my family we are using an "Family" apply id as a shared family account along with my account and my wife's account. We were using the family account to share icloud content between my wife and I and our family iPad. Under the family apple ID I had also created two alias email address (lets call then child1.me.com and child2.me.com) which I had done a long time ago to "reserve" my preferred emails addresses for when the kids were ready to have one. Apple has changed things a bit since before IOS8 and I have begun to disentangle the family account as a shared iCloud between my wife and I and we are now running our own iClouds, though our iPad still runs using the family account.

My daughter is 11 and recently inherited an old iPhone. I had recently created her an apple ID by faking her age and using her gmail account (as Apple would not allow under 13yr olds to have an account). One thing I discovered is that she cannot access child1@me.com account that is an alias of the family account so I started to dig into this deeper. Now that Apple has family sharing I thought I would delete the alias child1 and child2 accounts and set these up as proper apple IDs (as apple now allows this for kids under 13) with Family sharing.

I deleted my alias email addresses and tried to create the same as new icloud accounts (as apple does not allow the use of .me anymore) i.e. child1@icloud.com and child2@icloud.com. This is not working however. Apple is telling me that the accounts are already in use. My understanding is that .me and .icloud are interchangeable so my child1.me.com email alias should have prevented someone else from taking child1.icloud.com; correct? So it would seem that I am blocking my own icloud account creation even though I have now deleted those aliases.

Does anyone know when a deleted alias will become available for use as an icloud account? Also is there any better ways to achieve family email/icloud harmony as right now I am finding it a bit of a mess....

Thx.