Deal is two purchases, the first before 05/23, the second before 05/31 after you get the discount code from the first purchase.
BEFORE 05/23: PRE-ORDER SM Galaxy2 @ $49.99 to get $20 code email upon shipment on or after 05/23. Use "SAVER" code to get free shipping.
AFTER you get SMG2, and BEFORE 05/31:
After you get the SMG2 and the emailed $20 code, you purchase the New Super Mario Bros for $34.99 (sale ends 05/31) and use the $20 discount code. Use the "SAVER" code again to get free shipping. Assumes you get to use it twice, otherwise $3 shipping.
Expected net outlay: $65 ($50+$35-$20)
With free shipping for both games!