Thanks a lot Lampert Dias architect, ainslie, and edithsmom for your precious comments. I was so happy and excited when I saw your comments being posted up... Really appreciate it so much. My chesterfield measures about 210cm by 89cm by 75cm...hence I am not sure if there is still space for an armchair. I love the aviator chair from restoration hardware but probably have to give it a miss as the arm chair's length is about 100 cm . Any advice on any armchair that can go with the chesterfield? Or not advisable to put any armchair since the space layout is quite small?

just giving some opinion here. it would definitely look great with some cushions on it. Would recommend you to get from an cushion online retailer in Singapore called 1001cushion My favorite cushion from them is Garden Cushion & Metallic Cushion (Classy and Fresh) P/S: They are doing promotion of FREE shipping now.

I want exactly that sofa style, but in gray. My budget won't allow me to buy the leather that I really want. Do you know of a great place to buy this, or can you tell me how linen or bonded leather holds out? The room will be used for everything.

Yes that's a good idea as the 3 kids can have their own space. As the room space available will decrease, you may want to look into customised furniture so as to take full advantage of all available spaces. You can also consider a loft bed where you can place a study desk at the bottom.