He's still in highschool. He has a sister. Older sister to be exact. And sobrang masunurin naman nya to his mom. He's nice and all.
Ok, the good news, he isnt the only child, so its not very difficult to impress the mom. The not-so-good news, he is still unico hijo, so dont think that you'll get off very easy on impressing the mom
Remember, he is now the one that will carry the family name, so expectations may be high, like you said, he is nice and all, lalo na if he is an honor student. I'm not gonna say that you have to be up to bar, parents are rarely "mahadera" like in the korean novelas that we see. They do become protective, ONLY IF they see any negative vices on you (smoking & drinking, if he doesnt do either). Otherwise just be your natural self and show that you genuinely take care of their little boy.
Never compete for attention. The mom may call his kid to either take care of something for her, just remember your place at the moment, he is her son, you are the girlfriend.
At the end of the day, open minded parents arent gonna put you through hell just to impress them, just show your genuine self (it doesnt harm to dress presentable during the first encounter!) and show your real personality. Parents can see right through you (especially moms, since they are women) if you try to pretend like something your are not.