A site that is free to public schools and that is a small cost for parents is ABC Mouse.
This site is not designed for older children, but is fully inclusive to preschool up to kindergarten. Even though the age limits are a disadvantage, it is still a good site to use for smaller children.
If parents want to use this, there are payment options available where it can be month to month or a full year. This is one program to try with smaller children.