Also an AF parent, but I don't recall any NROTC parent saying there were two interviews. Centhea is NROTC parent, maybe you can pm them and ask.
I have never heard of a board selection interview for ROTC. Typically, boards convene at one specific spot in the nation for a couple of day.
I think maybe since you are new to the process you are thinking that there is a BGO interview and a board selection interview, whereas, the BGO is actually interviewing for the board selection. BGO/ALO/MALO's are liaisons to the board. They interview all of the candidates they are assigned and write recs regarding them for the board to review with their packet.
I also agree don't wear the uniform. Your DS's resume will have JROTC on it and he can highlight that in the uniform. Most interviews are in a casual atmosphere, thus, khakis, new polo or button down shirt with dock siders is the typical dress for guys. Don't have him walk in with holy jeans, graphic t and rainbows.
As a parent who went through this a couple of yrs ago, my only piece of advice is to remind him that BGO's are there as a support system to get their dream. They are not the enemy. You don't want him walking in stressed over the interview, you want him to be himself and you need him to understand that if he is himself, then the BGO will see it. Many times as parents with good intentions we create more stress than is needed. This is a scary time for him not only because of the BGO interview, but the entire college application, and silly little things we do can do more harm than good.
Only you know the line for your DS. If you see people here saying they are doing practice interviews at home, that doesn't mean you should. If you feel that he is someone who would benefit from that, than go for it. My point is there is no "perfect" way for every single candidate.
Now before you ask about questions here are the typical ones
1. Why the Military
2. Why the Navy?
~ If he answers because I want to do XYZ in the Navy be prepared for what if you don't get XYZ, what will you do?
3. How long have you wanted this?
4. Are you applying for USNA
~ Follow up will be why aren't you applying for USNA, or what if you get both?
5. Give me an example of overcoming a difficulty?
6. I see on your transcript you....this can be from having only 1 C in one class to the course curriculum
7. How do the folks feel about you doing this?
There are a ton of more questions, and many are candidate oriented to bond with the candidate...i.e. You're in La Cross, I always found that sport unique, isn't it hard to play football with a stick?
As I stated, you will not find one candidate on here that has had all the same questions for their interview, but most of them have had at least a few of the ones I mentioned.
I also know sometimes the Liaison likes to talk to the parents. Don't feel like this is the time to boast about your child, what they are looking for is to bond with you. Not every one does this, and the reasons may vary person to person on why.
As aglages and I say, this is not only a marathon, but it is a marathon that feels like a roller coaster. Your emotions will be all over the place. You will have a pit in your stomach knowing that board results are being released, and hopefully you will get it on your 1st shot, but many are deferred, thus your cycle of emotions start all over again. You will also repeat this process for all of the college acceptances. You just need to remember we have all walked before you in your shoes, and we are here to let you vent, brag and cheer you on, because next yr you will be the one holding the parent of 16's hand.
Best hopes, wishes and thoughts!