When I first started, I had a couple children with older siblings who would sometimes come if needed and I had room. I used to charge $10 less a day (which worked out to $20 in my case). Centres around here charge around $15 for full day school agers. IME, the older kids (as in 5+) are a big help around here and they like to help out and feel important. They were both older boys and they were so good with the younger kids, it was actually easier when they were here because they loved to entertain the younger ones so I got a break. I always told their moms that their older boys were going to be great babysitters!!
I only have one child now with an older sibling and mom did ask if I could take her for the summer but unfortunately, I don't have a spot available.
With being licensed and funded I charge the same as a daycare centre and the full date rate is the same for kids from 2 to 12 years old.