Help- legwarmers

so i have about 800= yrds of blouce yarn, probably a fine gauge yarn.( :shrug: ) i think i will need to strand it with another yarn for more warmth and better elasticity. i also don’t have a pattern so i was going to do the following (numbers are just random from an imaginary swatch :eyebrow: )…
knit all in the round
co 30
k3 p3 untill measures 1.5 inches
k all untill measures 15 from ribbing
k3 p3 for an aditional 1.5 inches
should measure 18 inches top to bottom
so what on earth are my questions…here i go :whoosh:
what yarn should i strand with? i was thinking lion brand kitchen cotton (for washability and long wear)
will my ‘pattern’ work? got a better one? (shes almost 4 btw)
can i just use two strands of the blouce? will it be elastic enough to stay up on her little legs??
:zombie: have i bored you enough? and am i just crazy?

THANKS!

KnitPicks has three new free legwarmer patterns that might help as a guide for you:

http://www.knitpicks.com/projects/projects_list.aspx?DGType=‘FP’&titleType=Free+Knitting+Patterns