I like Caron SIMPLY SOFT very much. It is a very nice yarn, affordably priced!
I looked online today, at other washable yarns...and one thing I found to be a problem...many of the yarns I liked did not have dark saturated colors nor cream or white colors. A decision about brand of yarn would be decided by the colors, and washablilty...in addition to the weight of the yarn.
I forget, does the original Christmas blanket call for worsted?
If it asks for worsted, would the motifs become distorted out of shape if we used dk or sport?
But, I don't mean to butt into this thread...I haven't even committed to knit the blanket! Sorry.
I might try ONE SQUARE of the blanket, as a swatch of sorts... to see how DOUBLE KNITTING and I get along! I'll use a dk and see how things pan out dimensionally speaking. You know, to see if it knits up SQUARE, and not rectangular. That'd be a bummer.