I have no personal experience in this matter. However, here are my two cents

Tell your bhinaju not to focus at all on his research work with UNDP and stuff. The counselor is probably going to ask him what he does for a living. So he just needs to tell the counselor what his profession is. It will be helpful if he is able to show that it is a permanent job with good benefits and stuff. Tell him not to focus on his educational qualifications much. Besides that I would suggest him to include some kind of a document that shows that he has two kids. May be a nata pramanikaran from the wada or something (just in case the counselor looks at it while flipping through the file). He should also include financial documents showing that he has very strong financial ties to Nepal.

Are your parents too attending your graduation? If not, it will be very easy for him to tell the counselor that you really wanted at least one member of the family to be here for your graduation, that's why he is applying for the visa.

Just out of curiosity, why is he applying for the visa?

Disclaimer: I have no personal experience in this matter. So take my advice with a grain of salt.