A top down/bottom up shade or draperies hung high and wide to expose the full window when open.

For now, for privacy, I’d just get inexpensive inside mount roller shades. Get moved in and situated and see from there. I don’t know your decor style to say more.

Curtains, Roman shades, solar shades, wood blinds, indoor shutters … lots of possibilities.

I LOVE the diamond panes!

Lovely space! I recommend a combination of blinds and curtains to treat this window. or just curtains, they all would be very good choices. Curtains from the top to the floor would be nice.

If your boys are sensitive to light, it would be better to use blackout curtains, which will also serve to protect privacy; Nicetown's blackout curtain is worth a try. If your boys like waking up with sunlight, you may consider sheer curtains, for privacy, better to add blinds.

About the color, black, beige, blue...just match the overall decorating style would be good. Or you can just ask your kids what color they want.

Hope it helps you!