What makes a batik a batik is not just the color method: it's the much higher thread count (therefore batiks don't ravel on the cut edges like non-batiks). Many guild members have mixed white tone-on-tone and white solids with batiks, and the unanimous assessment is that the two fabrics behave differently in stitching, blocking, and quilting and created some challenges using the two different thread counts.
If you look at batiks in general, the colors are very "clean," even those with grey. I'd assume that the plain white batik used for dyeing has to be a bright, "clean" white so as not to dull or influence the clarity or intensity of the colors. I'd order a FQ if possible of the white batik-for-dyeing to compare with the other quilt colors.
I might also consider a "white" batik that has some faint coloring or even a soft pattern to it: the plain white-for-dyeing batik may stand out unpleasantly against the other batiks that have more movement because of their color or pattern of dyeing. Go to
www.batiks.com (who is now shifting their name to "Batiks Etcetera & Sew What Fabrics" - probably as a result of a buy-out or merger) and look through the "white" fabrics there. The colors are pretty true on-screen, AND they also have a description of the pattern. There might be something of interest that's not white-white, but may offer a little something in the patterning or whisper of a complementary color. I looked a bit myself and found Hoffman J9000 White Pearl 3, Anthology 3552, and several Catik Batiks that might work better than the white-for-dyeing batik. I stopped at Cantik Batiks, but batik manufacturers list is MUCH longer.
GOOD LUCK with your search: only you will know what does the trick for the recipients of the quilt! [Psst - don't forget to have fun!!!]