Congratulations! Twins are so much fun!
Those are nice names, but they do not sound like they come from the same family...
Landon Parker is kind of a nice traditional laidback name, whereas
Galadriel Hope sounds like she might have stepped out of a fantasy novel. :-D BUT, kudos to you on NOT being too matchy matchy because that is one of my pet peeves with twins and is something I think way too many people do.
So if it doesn't bother you that they don't sound like they're from the same family, then go with it! Why not....