Same SE Account but Different PSN accounts for PS4, Can I do it if already tied PS3?

[WHS]

I currently have 3 players in same house using the same ps3 console. So I had this idea I would just use the same Square-Enix account and same Sony Entertainment account.


Of course we don't play at the same time on ps3, some of us use the pc and only one can be on ps3 at any given time.

For security purposes this all made since at first. Me being the Dad I wanted the token to be used and so we each have our own ffxiv account but its under that one SE account.

I don't mind sharing the SE account but with the online features and individuality of ones reputation online I am now thinking that my family might like to have their own Sony Account to play the game with. To use the messaging , chat, and trophies features.

I am willing to even rebuy the ps4 version if my family don't have to start over again. I need to take the ps4 key I get and register it to the ffxiv service accounts. I plan to buy at least 2 keys and will free upgrade the 3rd. I need to then take the brand new keys and keep them under the same SE account but put them on a different Sony account.

Can I do this? What steps do I need to go through to do it?

All in all this is what I eventually want it to look like:

SE Account - (FFXIV1-PSN1, FFXIV-PSN2, FFXIV-PSN3)

Same SE Account but different PSN accounts. This way they don't lose their time they put in and items. I was told they could start over but I really don't want to put them through all that if they don't have to.

One more question:

Can I choose a new PSN account at the time I register the PS4 Keys for the 2 accounts I am buying upgrades for? Or are they stuck under the current PSN account if they want to keep levels, items etc...?