when my parents go to sleep i put my fan pointed out the window, then i smoke and blow the smoke into the fan which blows the smoke out the window, and also helps air the room out. if your parents smoke or dont mind you smoking you can just cover the weed smell up with cig smell. but mine dont smoke so i have to be more discrete. as far as your eyes, just get eye drops or say your tired or something else that works (i am allergic to ragweed pollen so my eyes are red alot during this tiem of year :P)

but most of all, be alert, dont have your music blairing and the tv real loud. be quiet and listen for people waking up or coming in your area.