With the changing table right there, I would not do curtains (mom of four here). Too many opportunities for a mess.

Blinds and a shade are enough and I’d avoid curtains also due to radiator.

Make sure whatever you install in the way of shades/blinds/romans is CORDLESS!

Yes! Very good point!

Won’t it look ugly with just a pull shade though?

What about a blackout, cordless roman shade in a nice fabric? There are some here, or you get could a custom one from Etsy.

Another vote for Roman shade. Inspo from a Scandinavian curtain company below:

I would source Scandinavian nursery print fabrics for a Roman shade (cordless) and have it custom made for your room! Pretty, colorful (yes!), and modern.

If considering replacing completely thought the link below might be helpful. Have you considered placing the changing table on the wall on left, if you home is located where weather gets cold or damp. https://mini-magazine.com/nursery-window-treatments/

Unfortunately it’s too big to fit in that space!