Ahoy, Caroline!
it's a such a bummer to have that unbalanced and difficult to control feeling of vertigo. I wish it on no one, since I've had to battle with it, on off, in the past myself... and it is no fun at all. I've had to take medication in the past, and luckily, I've had no major occurrences. I do suggest taking it easy when you get back on land. I make it a point to not fly home on the same day as disembarkation. I'll book a flight home 1-2 days after we get back from the cruise just to get my sea legs back on land. I usually feel the rocking motion on land a few hours after returning - it's a weird feeling, but we've gotten used to it. I end up swaying left and right slowly for a few minutes.
Depending on where you are onboard, familiarize yourself with the nearest doors that take you out on the deck. Feeling the nice ocean breeze on Deck 4 feels very refreshing on the
Disney Magic. At the same time, your family can try their skills at shuffleboard, as you relax on one of the comfy chaise chairs :-).
Try hanging out midship in the lobby atrium as well... it is bright and airy there, and since you are right in the middle of the ship, the ship's motion is supposedly felt the least there. Deck 3 and Deck 4 midship will have very comfortable sofas and lounge chairs that overlook the beautiful atrium. I love hanging out there!
I hope that everything stays level and stable on your cruise vacation, Caroline!
Wishing you a magical voyage!
~ Dolly