Allowing your dog to sleep with your kids puts them all on equal playing ground. They might as well be littermates. Some dogs can be up on furniture and in beds with no problems while other dogs can get territorial over their space. This is very dependent on that individual dog but putting your child in a situation where the dog could growl/nip if rolled on or if the child gets up to use the bathroom and then comes back to the dog not wanting to move over could be dangerous. The dog should have their own sleeping space on a dog bed on the floor.