There is a distinction that needs to made though. If we are saved by grace, know God, his words, commandments and then fail to follow his commands and do good works to please God (not to please ourselves or to gain glory from God's works through us) then we are not really his children.
There is a big difference between God's children who choose to disobey him, and God's children who have not heard the good news and have not accepted him.
If on our death bed (such as the thief so to speak) and we hear the good news and accept Jesus and beg forgivness then surely God will welcome us into paradise until the day of Judgement.
So there is a difference between sinners that have never been found and God's children who have knowingly disobeyed God.
Remember, I am not a Biblical Scholar, but I am learning a lot as I study more and more.
You can argue 'til you're blue in the face about different denominations (see FreeRepulic.com ;-) Wesley, Luther etc...but the thief on the cross breaks it all down...
God Bless You! and have a great Thanksgiving.