With the room dividers, bed can be separated. browse here http://www.theclassyhome.com/comersus_listItems.asp?idCategory=293&Furniture=Room+Dividers

it' not the size of the toilet that matters, it's the size of the humans that need to use it ...allowing anything less than 80cm x 80cm for knee and elbow space, plus more for standing room plus extra for any swing doors and more space for a handbasins and with no other toilet on the ground floor the best option is a separate toilet and i would steal some space off the laundry to make a more comfortable powder room..and the different floor levels don't always prevent stealing some space off the laundry but what is the size of the laundry, including ceiling height at the wall closest to the back of the existing toilet and is the laundry ceiling flat or raked and how many steps are there between lowest floor and bathroom floor?

to ensure that the family room still has space for furniture i would alter the access under the stairs to a more convenient location and my plan also includes extra thickness in the laundry walls to enclose sound deadening insulation and a solid core door, a 650 to 700 mm deep counter will fully enclose the depth of the standard front loader washing machine and condensor dryer with underbench connection to water, drainage and power and a skinny tub (ie narrow from side to side) will allow for extra width for a 900 broom cupboard (vacuum, ironing board, stacked linen) all with or without doors to enclose the whole space although the sink could be included inside a wider broom cabinet and low doors could enclose the wm and dryer with 1300 wide open counter and wall cabinet left exposed.. details depend on how you like to work but there's plenty of space for everything you asked for and the arrangement of the bathroom depends on window location

Is there a reason why the kitchen is where it is? I would change the kitchen to be on the left looking out to the deck, then dining and living, all looking out to the deck, and put bedrooms where the kitchen is. Then the bedroom occupants would have some privacy, instead of having to walk past visitors in the lounge or dining to use the toilet or bathroom. You have noted that the red walls are existing, so I assume all other areas can be changed