I knew a girl who when in grade school they would sleep in a sleeping bag because she hated making up their bed. The problem was it was silky fabric so half the time she woke up on the floor after sliding off of the bed.
Here's a good idea for kids that reminded me of her - it's called the ZippySack and is a soft fleece with a Paw Patrol theme. It sells for $49.99 and if you sign up for the Bed Bath & Beyond newsletter you can get a voucher to save 20% off of one single item in-store.
Having a snug fit to the blankets can definitely make a kid feel more secure feel at night. No monsters grabbing out wayward feet, for example.
You can see from the images how the ZippySack works. It fits onto the bed like a fitted sheet, then kids climb under the covers after zipping it open. Making the bed is as easy as zipping it back up again.
Orders over $99 ship for free, otherwise shipping is $6.95. You may also order online to reserve the item for a free in-store pickup if that option is available.