They have activities at different times of day, depending on whether it is a sea day or day in port. Typically the first evening is set aside for signing up and getting an overview of what they will be doing.
Note that because of the age differences, your children will not be in the same programs and they normally do not make exceptions for the group age limits.
I cruised on Elation in 2010 and was impressed at how the youth programs appeared to be going. Of course that was 18 months ago and the staff can change. Carnival has an excellent youth program.