You have no idea how much we struggled with this. I thought wood blinds would be ok as well, but the room is in the direct sunlight all afternoon and a ton of light got in. Now, my daughter can sleep in a mildly dim room, but definitely goes down easier and sleeps better in a dark room. It's really less the light than the fact that they start to get inquisitive and social and want to see things (like the ceiling fan I painted stripes on in her room to match the carousel theme - she could look at that for hours even if her eyelids are trying to fall!)
Our solution for the moment is to prop a pillow on the bottom of the blinds and then a blanket above that. Not so svelte looking. And, I'm too lazy to take it down so the window is never letting the sun in. If I had it to do again, I would have gotten one of those honeycomb shades with the blackout lining. Would have made life much easier (but do be aware it makes a room hot in the summer b/c no air gets through, so you'll want to use fans or AC in the summer if you live in a warm climate!)
The other thing I'd highly recommend is a dimmer switch in the room. That way you can dim the lights to get the baby ready for sleeping and still be able to see if you need to sneak in and feed him/her or give them a pacifier etc. Bright light is just too harsh for them for a while. We had a night light over by the changing table area and kept the lights on a really low level dim for practically the first 3 months!
Good luck! :) March is such a great time to have a baby. My Maeve came in July and it was hot as hades. My best friend had hers in March and she was in recovering and going through the first month or so when it was still early spring and out and walking by mid-april, all May and into June. She looks great - for me, it was too darn hot for me and the baby to go anywhere until September!
p.s. I'm adding two things here: 1) there is probably some rationale that says you should teach your baby to sleep in a semi-dark room or else they won't be able to do it elsewhere - I don't know, I'll take sleep everyday over bad sleep a handful of times somewhere else, and 2) there are different intensities of black out blinds, so be sure to pick the one you want!