Iron as regularly as you are able, this prevents the clothes from getting dry and crispy which makes them harder to iron. An hour and a half or so once a week is about right for an average size family.
Tshirts and easy care items usually only need ONE side ironed if you use lots of steam. It depends on the cotton content, the more cotton, the more crumples usually. Then you may have to do both sides.
Buy easy care items for the kids, wrinkle effect clothes are great for you. Buy hubby work trousers without a crease if you can get away with it. If your hubby has to have a suit with trousers with a crease get them dry cleaned! Shirts especially should be ironed within a week or so of washing or they end up taking more time.
Don't make work for yourself though, do what needs to be done, fold it away and get on with your life!