Bonus buy with Coupon Article

We have created a promotion with a bonus buy on the Coupon article to target a group of customers who has senior cards.The bonus buy has 5% on the total sale of all article. When customer shows the senior card, sales person scan the coupon article barcode. then this group of cusotmer will receive 5% off on the total sale.

But now there is a business requirement to give this group of customer extra 5% off on a group of articles.

How can setup the bonus buy for this case?

Please HELP

Thanks