See ya later, alligator! in while crocodile! ?

i wanna know what is that movie this appears. its the story of a little girl that lives with her mom and her sister in a motel, they own the motel. and a lady and his 40 something retarted son came to stay there. the lady has cancer and is going to leave his son in a center. the man develops a friendship with the little girl. while the little girl's mom dies, and it turns out it was her grandma and her sister is actually her mom and she is scared that the 40 yr old guy will do something to the little girl..... i cant remember the name of the movie but i know... that's what he told the girl at the end and she responded in a while crocodile.