Some cruises do not allow small children on board, mainly for safety reasons as small yachts/catamarans have many open spaces and steep stairs that are not suitable for children to run around. Other cruises, especially the large vessels do accept small children on board and even have qualified guides and staff on board to make a magical experience for small children.
Most yachts/catamarans accept children over 8 years-old on board and offer special rates to children up to 11 years-old for cruises and flights as per availability and feasibility to accommodate a Family on board; with all cruises, it is required as pre-requisite to have parents sign a release form if travelling with children.