Led's don't pull a lot of power and don't make much heat, either. I think it'll be fine.
Yes, leave them out of reach on a normal basis
Go for it - but don't leave them on when you are out and turn them off at night!
I want to put some string lights in my room sorta like on top of my room like what most people do. and I know I would get LED lights. but would it catch on fire or something? Id like to buy them from target or walmart.