I confess I don't do the 'expectant father' thing. I make sure my ewes are fit and healthy, sufficient good quality feed, access to forage, plenty of good hay available, clean water and suitable shelter, then I let them get on with it. I avoid messing them about. I don't scan, it won't put a lamb in there is there is none. If one seems to be in trouble, I do what I can, but generally they don't need me fussing.
Due dates, just as with humans, is at best an estimate, they are not a production line in a factory, the little ones will come when they are good and ready to.
I keep Soay ewes, and they have thrived for many generations on an island without human intervention. One of the reasons I chose that breed is because they are hardy and independent.