The first time I went to my girlfriend's house, his parents didn't drink. Do they need a toast when they eat?
You don't need and shouldn't drink, it will bring you some bad factors. First of all, his family thinks that you like drinking, which will screw things up or wrangle, which is a bad omen. Second, your drinking shows that you don't care about your family, and that you are a fun-loving guy. I think it's best not to drink.