Yarn advice - super bulky cotton?

[Meli]

I knit my mother some lovely cabled hand warmers using Lionbrand's (worsted weight) Cotton-ease in avocado. I would like to knit her a matching cowl, but the pattern I found and really like calls for super bulky (http://www.ravelry.com/patterns/libr...ckenridge-cowl for reference). Could I use the same cotton-ease and just double it up? Would it be better to triple it considering the yarn? Would that even work for this pattern?

Any advice is greatly appreciated... my mother won't wear synthetic materials (shhhh don't tell her cotton-ease isn't 100% cotton!!).