I downloaded the pattern and it actually calls for a worsted weight acrylic yarn. The sample pattern shown in the original here
was done in Red Heart Soft. So I think that Simply Soft would work great.
Artlady, I think you are absolutely right about the color though. I've been looking through color cards online also and have had a hard time finding the colors I like as well. I was thinking Simply Soft as that's what's available here. I live about 1.5-2 hours away from any city and I'm not sure I'll get there before this KAL starts. I'll keep searching though.
I really like the original colors and would like to stay as close to it as possible. I also think that I'll just do the original star chart as well, because I really like it.
As long as I can get the yarn for this project, I will be joining this KAL!