lol, hate semi veggies! sorry, couldent resist. there are people who call themselves vegetarian and still consume chicken and fish, but to me (and probably the majority of whole vegetarians and vegans) I just think its wussy, n/o.
As for the wholes parents thing, I just flat out told my dad, but then again he already knew that being vegan wouldent kill me (high school girl friend) and he was like, whatever floats your boat. My mother on the other hand (dont live with so it didnt really matter) accused me of an eating disorder, and all that, practicly forced me into taking vitamins, but i was like whatever, lol.
I dont know your parents, so i cant really give you any advice except, just stand your ground i guess.
good luck and crongrats!