Why would you let anyone other than a trained, qualified, licenced medical professional touch touch your baby? Think about it logically for a minute - they want to do something to the bones in your baby's skull? There is no way I'd let anyone short of a doctor specialising in neurology to anything to my skull, let alone my baby's.
At best, it will be worthless expensive nonsense and you might benefit from some placebo effect. At worst, they could do damage to your baby because they have literally no reputable qualifications and no standards of care and no evidence to show any benefit. This explains it well. www.motherandbaby.co.uk/baby-and-toddler/baby-and-toddler-health-advice/cranial-osteopathy
From the child's point of view, pretty much all birth (except maybe a c-section) could be considered traumatic. Their skill moulds to fit your pelvis and has great forces exerted on it to do so. But this is the best evolution has come up with for us and there is no way some woo-peddler can do a bit of a head massage and counteract any of that. If your baby has some physical misalignment due to its birth or any other reason, they need a doctor and a physiotherapist.
Can you give some more details about your child's sleep, age, etc and some people on here might be able to suggest advice that won't cost you a penny and won't risk any harm to your child.