I use a free image editor 'Faststone Image Viewer' you can size them up & print them off any size you like. Knock 2mm of each dimension if you're goning to laminate the cards after.
If you're working with an image that has both the cards on you will have to crop each card out individually & save, also easily done with the image viewer.
When you hover the mouse over the print option in the menu, the design & print option should reveal itself. let me know how you go on mate but i'm just off out for a few hours now so won't be able to get back to you until later.
Good luck
John