Formerly the time tell the child that is a single mother son had no date, it was rather conceal the fact to always be considered a disgrace and many of these children grew up believing that they were sons of his grandparents and brother of the brothers of his mother.
Currently is thought to be the most convenient tell them the truth just the child begins to ask why his family isn't as their friends. Know the truth carried the child takes reality and take it naturally, for which it is necessary to convey safety and confidence in their future, not must be details unless requested by the child, and make it as it grows.
For a preschool isn't necessary to give many details simply that there are many types of families and yours is one that not coexists with the father despite that it has.
Schoolchildren will instead require a bit more in detail, know who is his father, how, where, etc., to be very important to tell you that he will be well cared for and loved, and will always have a good life.
Adolescents require greater care to the answers given because they tend to catalogue the facts and people with adjectives. It should be well clear that his family is a family type and there is nothing wrong with that, not should speak ill of the father and to the extent possible it positively. Don't let the opportunity pass and takes maximum advantage of benefits of grants for single mothers.