I would be surprised if there would be many children on a cruise like this. Usually on long cruises like this you find more mature people who have the time and money to go on extended vacations. What exactly was the episode of Samantha Brown and what scared you? The food and entertainment on the ship should be excellent, but on a cruise of this length you should expect some repeating. You will have the option to choose to eat a few meals in port for a change of pace, and to experience the local flavor. Which is the exciting part of traveling.
The wonderful thing about this cruise is it will be port intensive. You will see a lot of countries, and experience a lot of culture. It should be very educational. A cruise provides you an excellent way to travel saving you money over flying to a destination and paying in Euros for hotels and meals. The cruise is very economical especially with the children. I'm sure at times it may seem to be long, but then other times it will fly.
I think the children are a little young and won't appreciate the education they could gain from this cruise. But I think the cruise is a comfortable, safe environment for them, and much easier than trapsing all around Europe with them, packing, unpacking, dealing with trains etc. There may not be many children on board, but that also means yours would get more undivided attention.
Hope this helps.