Try making the transistions with just his day sleeps only for a week so at least your still getting a good nights sleep. Then you can introduce it over night. I too would try just one arm at a time.

But i wouldn't worry too much I've worked in Early Childhood for over 12 years and we would happily rewrap babies, we try to follow your home routines as closely as possible to make your babies care consitent. I have often had to do the one arm wrap with babies coz this is what mum and dad are doing at home, most carers should want to do it as the care for your son should be very important to them as should be his indivdual routines!!!