Open this link. There is a lot of info for a new member. Look for the link to the Recruit Training Command. Just underneath that is a link to the Family Guide. Click on this and print it out for reference. This is a publication from the Navy. There is a section of Military ID.
If your dad is not retired with retired Military ID, then he must be on the Access List to attend without waiting. See Military Personnel Attending PIR Information (clickable link).
a VA card is only used for medical care at the VA, it is not a card showing he is retired or active duty. So as was said he will need to either be on the list to get into PIR, or he will have to wait to see if there is space for extra guests.
Special access is only for those who are retired or active duty. Dependents and those with VA cards do not count.
It really is up to the soon to be Sailor who gets to go to the PIR as they are the one who puts the name on the list while they are in bootcamp. Yes he does need to make the choice.
Also there are no assigned seats once in the hall, they are first come first serve
They VA card is just that, from the Department of Veterans Affair, not a DOD Department of Defense card. BIG differernce!