The only way to do it is if you're staying multiple nights then you can make separate but consecutive reservations - do 1 night prepaid FHR to get the $200 plat credit and the 2nd (or more) post paid. You just have to make sure the post paid portion including anything charged to your room will total $500+ to trigger your Amex offer. Also, don't expect/demand to get two of the $100 FHR property credits as that's against their terms and is considered gaming their system (if you're offered it, you just graciously and quietly accept it but if they tell you you're not eligible you obviously don't try to fight for it).