We are not able to determine who the elect are, for sure, because even the devil can present himself as an angel of light and quote scriptures. King David got himself in trouble with God for trying to number Israel, and Israel suffered greatly. It is a lengthy event that is portrayed in 1 Chronicles 21. If all of the twelve tribes are a part of Jacob/Israel, then, Yes, they will enter heaven. I believe "the kingdom of God" has reference to Christ's church, which he is the king and bride of. An example, in this day and time, of God's children worshiping other Gods; When any of God's children buy themselves a brand new sports car and spend all day on a Sunday polishing it up to show it off, That car becomes another God to them that they worship. There are many ways that a child of God can worship other Gods.
So, you don't know if you are an elect?