I did Windsong in 93 and yes you do really feel the motion. There were a number of folks who were ill some days. It was truly the best cruise, the best vacation of our lives. It was perfection in every way.
In answer to your other question about kids onboard- I think that they would be the only children- and you would most likely suffer some intolerant looks of others. It is a cozier atmosphere on deck than on larger ships- and the conversation and activities are really geared more towards thirty-forty somethings, honeymooners. I have children but feel that the atmosphere was definitely not geared towards kids, and as much as I would like them to enjoy French Polynesia, I would want to save the most romantic itinerary in the world for just me and my husband.