With infants it's not going to be the baby who may 'hate it' (boating).. They really don't care where they are as long as their needs are met. It's the parents' ability to adapt that will be key, and probably most especially the mother's.
A child will sense and key on a mother's anxiety, which can ramp up that anxiety and you'll have a vicious cycle. Trying a simple overnight at the dock is not a bad idea just to work out some of the logistics, but you'll still have to think through/and do the 'underway' part of it too, of course.
1984 Fast/Nicholson 345 "FastForward"
".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)