It is beautiful as is!
No, don't edge the 'crosses' with any color. If you edge them, place running stitches right next to the edges of the cross, in the same color as the blanket. Maybe a silky yarn, but in the same exact color. There are some DMC Pearl Cottons that have a sheen, and if used double would define the outline of the crosses nicely.
I think edging them with any other color would be overkill. Let the crosses be understated. It is a classier look. White on white has a purity to it.
Your Sugar n' Cream yarn looks white, but maybe it's cream, or a light light light pinkish? Regardless, my 2 cents stands the same. SAME COLOR for the outlining!
Great work, whatever you decide to do!