Dress Factor Fabric

My fabric for my dress factor dress arrived this morning. It's a lovely light cotton printed with polka dots in red and white.

However, now I am faced with a dilemma. The white fabric is translucent and I'm worried the seam allowance may show as they are quite complicated curved seams. So my question is - Do I underline? Do I line? or do I do both? What do you suggest? I know what i'm erring towards, but would like a few different opinions on this one.

Another quick question - I think I know the answer to this one - How would you finish the seams on the curved seam lines?