Why don't you knit up a swatch to see how you like them together? My only concern would be that the malabrigo may look a little out of place in the middle of all of that Nature's Wool Bulky. Of course, until you actually see it, you won't be able to tell.
Meghann is a Double Shot of Awesome!
OTN - too many things at once (if that's possible).
FOs- knitty's "back to school" for the sister, and lots of single socks (I'm a repeat victim of SSS).
"If all else fails, stop using all else."