I'm trying to decide whether to buy a sleep sack for my son (20 months) for the coming winter, or what. I think we should. My husband keeps talking about getting him used to sleeping with blankets. I have no idea how or when to go about that, but now seems too soon, because he a) still stands up at the rail of his crib crying for a minute before he lays down to sleep and b) rolls all over the crib. The few times we've tried to put a blanket over him (away for the weekend, colder nights than anticipated) he's ended up tangled up in it and crying in the middle of the night. Can anybody share with me when they introduced a blanket at night, and how they went about it?