Most cruises during Easter school holidays will be heavily booked so your biggest problem is finding a vacancy. Phone the number at the top of this page or go to the home page and select cruises for April. There are 10 day cruises to Canaries from Southampton (P&O Oriana dep 8Apr).
Ocean Village are very Kid friendly, they have organised activities and kids clubs. They also have a baby sitting service. They also do childrens menus like burgers and chips.
For kids, especially this age group, I would recommend Royal Caribbean every time....excellent children's facilities, organised "Adventure ocean" for different age groups and if you choose one of the large ships (Independence of the Seas, Voyager etc) there are loads of activities for everyone, including a water park, ice skating, mini golf, excellent shows. On the food front, RCI have self service with choices to suit everyone, seated dining with a varied menu , burger and pizza bars etc. One piece of advice though is to check the age groups for the kids clubs as different companies split them in different ways. e.g some have 4-6 and7-9, or 5-7 and 8-10 which should be fine, but some companies (not sure if it's P&O or Ocean Village) do age 2-6 - which for our 6 year old is a no-no as he doesn't want to be with the "babies" Check out the Royal Caribbean website and look under "ships" for the facilites.......I think it's "Freedom class" ships which are the bigger ones. Generally the larger the ship, the more kid's facilities there are. We are going on Indepence of the Seas this July with a 6 year old, mum and grandparents. Another posssibilty would be P&O Ventura. Both Ventura and Indy sail from Southampton. Would also be worthwile reading the reviews on this site ...put in a search for children to get the relevant ones....good luck and happy cruising!!
Although most major lines cater very well for kids, RCI surely has the biggest range of facilities on the water for the younger age group.....Wilba.