In my opinion, if you must discuss with them (i.e. if you feel compelled to meet with them) staying off doctrinal issues would be the wisest course. It is the course I did not follow. If you don't make the choice to avoid the subject, I want you to be ready to argue your point.
Psalm 37 uses a Hebrew term for "earth" that mean "land, country, earth, ground, etc." It is pretty plain from the context that the Psalmist was referring to the land of Israel. Particularly is this the case since the text frequently refers to an inheritance of and taking possession of the land. This 37th Psalm was written for a nation conquering its promised lands.
You might try getting them to think of the temporal context it was written in. 37:11 says, "And just a little while longer, and the wicked one shall be no more; And you will certainly give attention to his place, and he will not be." You could read that and ask whether it is reasonable to suggest that "a little while longer" actually meant 3,000 years and more later.
You might even be able to conscientiously bring up that while all Scripture is inspired of God and beneficial, all Scripture is not to have prophetic significance for every time period in history. Then you could ask why they would insist that this is going to have a greater fulfillment on us? If they bring up Isaiah, direct attention to the fact that the prophecy was for the nation of Israel, and that no Christian is recorded in the Scriptures as having moved that prophecy forward. Then ask: What is the basis for believeing it would have a greater fulfillment in our day?
But, I would recommend sticking to the discussion of "paradise" itself. In the NT the term only occurs 3 times. (Luke 23:42, 43; 2 Corinthians 12:1-5; Revelation 2:7)
In 2 Corinthians, Paul equates paradise with third heaven. Their explanation of "third heaven" is convoluted, grasps for thin air, and is easily dismissed as having no basis in Scripture. Also, it does not change the fact that "third heaven" is "other than earth," even by their explanation.
The Revelation Climax book says of Revelation 2:7, that this reference to paradise is a reference to the very presence of God in heaven. Noteworthy is the fact that the "tree of life" is pictured in this paradise of Revelation 2:7. In Genesis, fear that Adam and Eve would find the tree of life was the reason God expelled them from Eden.
In Luke 23:42, 43, Jesus tells the evildoer that the evildoer would be WITH HIM in paradise, not that he would be with the evildoer. In context, the evildoer didn't ask to be remembered "today," he asked to be remembered when Jesus got "into [his] kingdom." After that request, Jesus response would only make sense if he was welcoming the evildoer into his kingdom WITH HIM.
Given that a connection to heaven is implied in all three occurences of "paradise" in the NT, there really is no basis for belief that the 1st Century Christians believed paradise to be anything else.
I hope this helps.