Post-mortem evangelism seems to be a theologically sound doctrine.
1 Peter 3:19
19By which also he went and
preached unto the spirits in prison;
1 Peter 4:6
6For for this cause was
the gospel preached also to them that are dead, that they might be judged according to men in the flesh, but live according to God in the spirit.
Romans 8:38-39
38For I am persuaded, that
neither death, nor life, nor angels, nor principalities, nor powers, nor things present, nor things to come,
39Nor height, nor depth, nor any other creature,
shall be able to separate us from the love of God, which is in Christ Jesus our Lord.
John 4:24,25
24Verily, verily, I say unto you, He that heareth my word, and believeth on him that sent me, hath everlasting life, and shall not come into condemnation; but is passed from death unto life.
25Verily, verily, I say unto you,
The hour is coming, and now is, when the dead shall hear the voice of the Son of God: and they that hear shall live.