I second patricia, make it all the same flooring. I did the 'wood floor in the walk in closet' while the rest was tile, ended up taking it out and just tiling everything, the threshold was collecting dust and grime and annoying for my laundry cart.

No experience with babies actually - but seems there are endless combinations - this was just the first / type in and select "Stories" for good articles like this with at least 2 ideas. Many "Photos" on houzz. "Shop" too. [https://www.houzz.com/magazine/guest-picks-desert-beauty-for-the-babys-room-stsetivw-vs~29205805[(https://www.houzz.com/magazine/guest-picks-desert-beauty-for-the-babys-room-stsetivw-vs~29205805)

hi, in 2nd plan if you make upper floor in future your stair will open in bedroom (if you follow same layout as shown) if not then you have to make 3-4 feet wide corridor along staircase. Not a working plan.

You can buy any modern sofa. It will be suited for this space. Below I have added some of the best sofas (Oriental Creativity). Hope you will like it.