I think it is always important to understand who is providing a review on this site. There is such a diverse community of cruisers that perspective is extremely important. We are a 40-something couple with two young children, 5 and 4. We have done quite a bit of cruising with our children, we always focus on the itinerary first.
Harwich - Just one observation regarding departure - take the train! Unless you plan to tour England a few days before the cruise, driving in England (particularly this route) is very slow and difficult. Google maps quoted a two hour drive, it took us four hours due to heavy construction on the M25, pretty much the whole way around London. The train station is literally a hop, skip and jump to the cruise terminal.
Since we were the last folks to arrive in the cruise terminal, check-in was smooth, quick, and easy. The ship design is generally pretty lackluster, and shows its age. The process of "Solsticizing" this ship lead to a lot of questionable design changes. For instance, the kids club took over half of the forward nightclub, the Constellation Lounge.