We jumped in feet first for our first cruise with a week long Eastern on
DCL! About to take 5th cruise (all DCL!) this weekend!
This week's trip is a 4 night - wasn't planning on taking another cruise so soon, but couldn't pass on the special pricing they had going!
Take a look at the Navigators available on the FAQs on this board. They are samples of the daily itineraries you would have - see what types of activities on board that your family might like. Look at the available ports and shore excursions that may interest you.
re: sea sickness, I am very prone to motion sickness (even the rides at the parks!). I always take bonine starting the day before we leave, haven't had a problem!
Our first cruise was very rough waters, DH even took the free motion sickness meds they handed out for queasiness. We were fine that week as long as we took the meds. Other cruises, haven't really needed it. Also on that first rough cruise, one of youngest got sick the first night, but immediately after that episode, was ready to go back out and was fine the rest of the week.
Consider a 7 night! We treat the ship like a floating resort; very easy vacation, no running around!
On the other hand, on the new ship in 2011, 5 is the most nights that will sail - we're booked for that!