I did something that was cost-effective, but only partially worked. Bought two-inch wide black ribbon and draped it over the curtain rod holders and down the sides - then I pulled it tight and clamped it so it wouldn’t move at the top. I weighted the ribbon at the bottom sides. It kept out more of the light, but wasn’t perfect.

You are a good person and I'm sure your family is super proud of you! Such a thoughtful thing to do.

You can probably trim those off using a small pair of nail trimmers. As for drilling new holes, I like Tolenkanor's suggestion.