How do I make it comfortable for them? They have trouble moving about and have balance issues too.
It’s very important to get the colours right. Choose shades and hues that are bright, but not too overwhelming. Warm and rich shades of brown, gold, orange, and yellow ochre should do the trick. Better still, ask them if they prefer any specific colours. Nothing would make them happier!
Make sure the bed height is appropriate for your parent’s height. When they sit on the bed, their feet should rest on the ground without over-arching the knee i.e. the knee should be at right angles to the floor. 20 to 23 inches high from the floor to top of the mattress, is the recommended height. A handlebar to support them rise from the bed is a good add-on.
Avoid smooth tiles! Anti-skid flooring options like laminates and wood should be good. Or, you could get the whole room carpeted! Avoid smaller rugs and carpets, since there’s always the danger of tripping over them.
Absolutely minimal furniture - only the essentials, and with a lot of free space to move about. A wardrobe, a side table, and a reading chair, should suffice. Also, drawer and door handles should be levers and not knobs.
Make sure the room is airy and bright, with emphasis on natural light. You can have some additional lighting in the form of bedside lamps, and dim night lamps.
If your parents don’t mind it, and if there’s enough space, add some indoor plants too. They act as natural air purifiers.
Also, have grab bars installed in the bathroom.
My suggestion is you don’t put any heavy things like design, anything which doesn’t give freshness. Keep plants pots outside of the house. Space which gives fresh air.