A nand backup is an image of your nand at the moment it was made, including whatever game saves you had. If you restore nand without making backup of your CURRENT game saves then they will be LOST because your nand will be wiped clean and rewritten over with the back up nand.
Use a partitioning software that support editing exfat partition, use its cloning function to duplicate the old sd card byte for byte to the new one. If there is left over space then you can expand to fill the unalocated space.
Sweet I ordered the exact same dongle with the $4 off new user coupon. Also took nearly 2 days for status to change to shipped which is only 2 days ago. I guess I'll expect it to arrive next week.