I don't have meetings with the parents but if I felt it was needed I definitely would. For the most part, I just deal with issues at pick up time but if an issue needed more time or private time than I would schedule a meeting.

I have the same problem as you in regard to an almost 2 year old who is getting 11-12 hours sleep at night still. They say he naps at home but I really can't see it. He will lay in his playpen here and nap maybe 30-45 mins on a good day. He does lay in his playpen quietly though (now that I removed him from the nap room!! He naps in the dc kitchen) so I'm thinking he probably just rests in his crib at home for naps. I have mentioned this to the parents like "wow, he still sleeps that long? That would explain why he doesn't nap here." It brought on a conversation about what is typical for kids his age. To my knowledge they still put him down early. IMO, it is not my place to flat out say "You need to put him down later so he naps during the day for me" but if you feel that is something you want to discuss than that is up to you.

The sibling thing, I think you are right to request your transition the way you want. If mom doesn't like it she is more than welcome to find another provider. This is one of your policies and by the sounds of it, one she has known about for a long time. I am confused though why the money would be different? She likely wants them to come on the same days though so that she gets her last two weeks before going back to work as a "holiday" and that is understandable too but if you don't do your transitions that way than stand your ground.