585 square feet is an ideal candidate for a split mini system. First, it eliminates need to install ductwork, which may or may not be a big deal depending on access. If you are in a climate where a heat pump will suffice for heating, a heat pump system will work well. You cannot adequately heat and/or cool two rooms with any kind of wall or window system, due to lack of air circulation.
With the mini split, you would of course choose a flex multizone unit, with an air handler in each of the bedrooms, and one in the living/dining/kitchen area.
If you are in a cold climate ( below 30º) then you need better heat, and will need to consider a full size system , with electric heat air handler or gas furnace.