(1) You can pack your suitcases in the second morning and go out for your planned trip. Legoland staff will move your suitcases to the new room when it is available. When you back at night, you may check your new room number at reception. The new room will have new lego gift.
(2) You can pack your suitcases and place it to their store room (at the lobby). When you back at night, you may check your new room number at reception. The new room will have new lego gift.
Seems option 2 is more secure, I choose this one.
I booked Legoland Hotel via their offical website (during promotion).