No, 'tear up' would be if she was pulling the pages out of the book. You actually used a more appropriate verb (to grab) before you tried to form the sentence, so it would be 'don't grab the book.' Although I've always been told when looking after my cousin that I should keep the message positive rather than negative, which means avoiding saying things like 'Don't do X...' But I digress. We say 'turn the page' not 'flip.' It would also be an 'instruction', not an 'order.' You can say 'sit on my knee' (the singular is much more common) or 'sit on my lap.' Lap: "The front area from the waist to the knees of a seated person." As for lay down vs lie down, someone else can tackle that one.

The lay/lie question is very controversial , because basically no one uses the grammatically "correct" form for ex: "I lay down in bed last night" is supposed to be correct past however what we actually say is "I laid down in bed or I laid in bed" So if you want a technical grammar answer below I posted a link . If you want a practical answer we say same thing for both place an object somewhere and in reference to reclining : I lay / laid / have laid/ am laying on the bed. I laid some more gravel on the road. as well as sometimes using the correct word for "to recline" Sometime I lie in bed awake.

hey! So 'sit down ON my lap' would be used more if you were crossing your legs. 'Sit down on my knees' isn't so common but you would use it if you were maybe sitting on the edge of the bed. Yes, you could say 'Don't tear up the book' or you could just say 'Be gentle'. Instead of 'flip the page' it's 'turn the page' 'Time to lie down' - LIE is present and it means to assume a flat position on a bed, for example. 'Lay down' is wrong and doesn't refer to any bedtime position. You would say 'lay the pen down on your desk' meaning to put the pen down but you wouldn't use it for a person. If your daughter wants to have a little English lesson with me, I would be glad to help. I have been an au pair before and taught English to small children. Good luck!