I think the community centre should choose the swimming lessons for children.
Swimming is a very important skill, especially in Canada because there is many lakes and people go to cottage in summer. Every year we hear news about kids who drown. If children learn to swim when they are young, they will be more safe all their life.
Also swimming lessons are expensive now. In my family we have three kids and for one session it costs more than $100 for each child. We can't pay it for all of them, so only my oldest son took lessons. Many families in our area have the same problem, specially new immigrants.
The fitness classes for seniors is also good idea. My mother is 70 and she likes exercise. But I think seniors can do exercise by walking in the park or at home with videos, they don't need a special class so much.
For these reasons, I choose option A.