Will I be sinful if I conceal my wife and children, knowing that the imprecation (li'an) will cause great discord and killing, because those responsible for the sorcery are from the family?

The repudiation of a child is conditioned on it being immediate, unless there is an excuse determined by the Sharia judge. The court is the one to decide if sorcery is an excuse for repudiating the child now.

If the wife repents, concealing her (sins) is required and rewarded. If she does not repent and continues in her state, then remaining with her is a forbidden act of cuckoldry (dayatha).

It is not permissible for you to repudiate the children or harm them before a court ruling, because they are legally your children, as "The child is for the bed." It may be imagined by someone afflicted by sorcery that he did something when he did not, or that he did not do something when he did, making it difficult to be certain about repudiating his children.