Generally speaking-I'd go with curtains here. Easier to open sliding windows, easier to keep open/shut/half way open..I think the room will benefit from longer vertical treatments..unless of course the windows are so wide-and you mention them being big..that standard panels won't work and you're into custom territory. If you can sew-that's one thing..if you prefer it being made for you-very expensive, and it's cheaper to go with shades, even though these also will be semi custom, cut to size and all. If going with shades-I'd also examine smth like woven ones. They give this feeling of warmth, almost like fabric does. Depends on one's style of course, but you seem to prefer fabrics, and cozy feel. They come in different colors(limited range but still a range) and textures differ too.

There are several people here that are especially knowledgeable in evererything window treatments..I hope they see the thread too, and chime in.

Cellular shades are really plain and boring. I think you should go with draperies or roman shades (woven or fabric). Check out the Shade Store for ideas.

I think roman shades on the large windows will be hard to pull off. If I you had one for each window panel I think it would be difficult to keep them even. If you got one for the whole window it would be very expensive.

Target and Ikea have decent inexpensive curtain panels. Two panels for each side of the big windows so they look full and can close fully. Hang them high and wide. I would get them fairly close to the wall color, possibly with a subtle pattern. If you go too bold, all those panels will dominate the room.

I think the small window could be enhanced by drapery. If you hang the drapes so they stack outside the frame it will give the illusion of a larger window and balance with the others. I would really need soft lines in that room as well as some color and pattern. DH made wood valances for all my open concept room windows, and I have drapers under them. If you don't need privacy perhaps I would have gone with just the valance on that window if I thought the drapes were too much? I am just not a fan of shades outside of bedrooms. I agree the windows tend to be too large for them.

I think drapes are the way to go and they add a lot of softness to the space . As for furniture since there will not be a TV I would do 4 chairs around a nice coffee table , you need one to put drinks on feet on it itis nessessary. You could do drapes in the LR and a roman shade in the same fabric on the smaller window. Toddlers need to learn not to touch everything and they will soon not be toddlers so get what you need for the space and that includes a coffee table and some lighting somewhere.