We have crossed the Atlantic many many times usually in December when the weather is very unpredictable but have always been ok. Deceber 07 it was bad both ways force 10
but we made sure we had a supply of sea sickness pills and rather than chance it took them we were fine so I'm sure you will be. Have done Transatlantic in April and I seem to remember it was pretty calm.
I have crossed the atlantic on ov1 and found it very relaxing as the ship has stabilisers. it is never very chpppy but can get very windy but there is nothing to worry about.the six days pass quickly as there is lots of onboard activitys enjoy your cruis.