Just replace the cellular/duette shades you have with blackout versions. If you get the same brand, you can probably reuse the current brackets. Keep the current ones to reuse when you don't need to darken this room any longer.

Don't go over board on trying to black-out the room. My second baby did much better than the first, as we weren't as militant about trying to create a perfect sleeping environment! Baby #2 took his naps in a bright dining room with life carrying on around him ... he slept much better than baby #1 in a perfectly blacked out and sound proofed room!

IMO blackout for a childs sleep is the same as everyone having to be quiet when baby sleeps . In my experience baby's do best when life goes on while they nap and the sooner the better I agree so good blinds to keep it less sunny but I do not think blackout is a must.

Any opinion on white shades vs a tan tone or just the look of curtains in general?

You have white trim, so white shades disappear when raised up and not in use.

You have a lot of furniture in this room, so curtains will probably get in the way of something.

Every baby is different. My son needed total darkness so I did roller shades and blackout curtains. And a sound machine which he still uses today.

We did cellular shades that have both blackout and light filtering option on them. i don’t love curtains in baby rooms.