Wow, that's a lot of money to pay for daycare! $2,400 a month is almost my whole income! But I charge $150/week so $600 per month usually when there are 4 weeks for one child. I know Calgary is a more expensive city to live though and I understand. I would not reduce my rates for siblings but then I am at the low end of the scale.

You do what is right for your peace of mind and business sense and knowing what people pay in your city and don't feel guilty for running your business. The two previous posters made great points about not letting any other parts of the contract slide if you do allow a break in the price for this one family and making sure you don't have rates too high that you don't lose clients.