The tourist card allows its holder to stay in Cuba for 90 days from the date of entry into the country, and is valid for 1 entry into Cuba. For a stay of more than 90 days, one can request an extension of another 3 months at any tourism office in Cuba, for a maximum stay of 6 months.
Children, regardless of their age, also require a tourist card, even if they are registered on their parents' passports.