JoAnn Fabrics has Casa Satin, Hancock Fabrics has BFF, and general places have bridal or duchess satin - it's all about the same thing, and definitely what I recommend for princess dresses.
I wouldn't make a whole second skirt for the ruffle, I'd just add another ruffle to the bottom of the main skirt.
The skirt pattern I like for big hoopskirt dresses is McCalls 4090: http://mccallpattern.mccall.com/m409...hp?page_id=493
I've used this pattern for many big dresses and it easily fits a hoop underneath. The bodice and sleeves from the first pattern may work just fine, but I don't think you'll get enough poof for Daisy.
Also, I have a few tutorials for Peach costumes on my site. You may find some tips for Daisy.