Find out what your local schools are charging, if they have programs there.

Most of the schools here are charging between $21-$23, including a snack. So I would charge $20, and emphasis the smaller group and the chance to do different activities, as opposed to being let loose in a gym day after day with 30 other kids.

I'd agree with your thinking about Bill 10 as a factor too - if you can get a full-time 3yo, taking a sibling would probably be worth it.