I had always heard that children have much fewer problems with seasickness than do adults and that has been our experience. On both of our Disney cruises we travelled with many children (ranging in age from 15 months to 10) and none of them ever had a problem (though a few of the adults did from time to time). If you are greatly concernced, talk to your pediatrician and he/she can offer specific advice .... but i think you'll be fine! (and i have heard that green apples and gingersnap cookies can combat seasickness ... and getting kids to munch on cookies is usually an easy sell, so that might be a good preventative measure).