Interestingly, Marriott Rewards Mall has a link to Staples.com that says when you click through their link you will automatically get 2 pts/$1 spent on purchases made at Staples when your Marriott Rewards number is included with your purchase.

I wonder if one could follow OP's proposed plan of action, but purchase said cards via this link initially to double all that follows... (this may be convoluted as all heck, I haven't had enough coffee yet!)

(link mentioned above - https://mrewards.shopmyway.com/shopNow.htm?plc=4511& )