For myself I use Bonine. It is non drowsy, and I take one each day, works for the entire day. I get queasy everytime I cruise if I don't take it, so I take one before I board the ship, and then one each morning after that.
I have never had any side effects from the medicine, and I spend too much on a cruise in money and time and planning, to ruin even a few hours feeling sick!
As for kids, it is best to ask your doctor. I gave my boys 5 and 7 a 1/4 of a regular dramamine the first day, (told them it was a vitamin) I didn't want them to know it was for seasick, afraid that if I put the thought of seasick in their mind, they would start feeling it.
Anyway, they never even commented about the motion of the ship, so I didn't give them any after that.