Okay.......one more question.....or two

Does anyone have an opinion on the choice between an NCL (we're looking into the Sun) vs. Carnival cruise with our little boys (ages 2.5 and 5.5). Also, if we chose Carnival, is cigarette smoke a big problem on the Inspiration? (i.e. should we chose the Paradise? Normally, smoke doesn't bother me unless its around constantly).
The prices we got for NCL are a bit more expensive - so I'm just wondering if the extra $$$ is worth it.
Also, what about the Norwalk virus. I saw in the news a ship got sick again last week. Are little ones any more susceptible than grown-ups? A couple of my mommy friends really pooh-poohed my idea of cruising this spring because of the virus . . . so I'm just wondering how others were feeling?
Thanks for helping!..............Camille