You will have to be extraordinarily lucky to find five J seats to/from Europe at the beginning of peak season on AA at their saver rate, which is 57.5K per seat each way. That's 575,000 miles in total. AMEX can transfer to BA, which will let you book seats with *significant* taxes + fees for each ticket, but they also won't likely have five seats available in J.

Your best bet if you want to do this would be to hope a fare opens up. TAP flies from Miami and pretty routinely offers flash sales on cash tickets that drop the cost of flights from the US to Europe around or even under $2000 RT. You can try booking this through the AMEX portal and using your AMEX points to help defray the cost out of pocket, but that's your absolute best bet for getting five RT seats in J.