While most of the important points have already been touched on - I’d just like to reiterate a few.
Can you do this either way? - Yes
Would separate licenses have the same subscription and upgrade conditions either way? - Yes
I personally suggest a secondary Blizzard Account - under YOUR name for minor children for a few reasons.
- If a license is later moved, any collections stay behind on the original Blizzard Account.
- Parental controls are a very handy tool - but they impact all licenses on a Blizzard Account. Should you wish to use them, they’d also impact your license on the same Account.
- Security can be managed better with two Blizzard Accounts.
- It is a far simpler and cleaner process to get a Blizzard Account of a minor switched over to them when the time comes.
- Licenses on the same Blizzard Account have some restrictions - mainly pet battles and messaging - depending on which license logged in first in a session.
- While two licenses can be logged into from the same Blizzard Account, there is a little bit of logging out of the launcher, etc., that must be done to accomplish that. Should the second license log in without going through the proper steps, it can knock the first one offline.
Just setup another Blizzard Account with another email identical to your first, use that to apply the new license - and don’t forget to RAF it!