Thanks for the replies. To answer some of the questions:

It will four tickets, 2 adults, 2 children ages 13 and 9, probably coach.

I am the owner of both AMEX cards. The Gold card has a second card on the account that my wife uses. The Gold and Blue points are not connected but I will go ahead and call them to join them.

The VISA participates in world points.

Is it easier to perhaps purchase the trip out to Amsterdam and then Greece together using the AMEX points which I would transfer on a frequent flyer program (once I pick out the airline to use) and then buy the return trip tickets from Greece to the US using the World Points?