Hi Gerard,
You can use the wjecf_bogo_product_amount_for_coupon filter for that. Please enable multiplication of the coupon, set min amount of matching products to 50, enable BOGO for the cards and use a snippet similar to this:
add_filter( 'wjecf_bogo_product_amount_for_coupon',
'wjecf_bogo_product_amount_for_coupon', 10, 2 );
function wjecf_bogo_product_amount_for_coupon( $amount, $coupon ) {
if ( $coupon->code == 'COUPON_CODE_HERE' ) {
$amount *= 25;
}
return $amount;
}