Wow! Ok, the 2.5 year old girl is manipulating you and I suspect she gets her way with Mom & Dad all the time too. Cut it off and put your foot down and let her know how things are going to be from now on, she stays in her seat at mealtime and don't worry she will eat if she's hungry, she stays on her cot the entire naptime quietly, etc. No special circumstances for her any more. Use a stern face and a stern voice, be tough. It may take a few weeks or months but it will pay off.
Tell the Mom with the next two children that they must arrive by 9am and be picked up after 3pm. That's in my contract and I charge full day fees for that. I have a schedule to maintain and I deserve my break at naptime to recharge my batteries. Are you even getting a break at all during the day? It doesn't sound like it. With all our work after the children leave we are working 12 hour days or longer, so put your foot down there too. These clients are going to BURN YOU OUT!
If your own children want to sleep in their own beds I would definitely arrange things so that happens. Again, be stern and shush them and it will take some time to get them to realize you are not backing down, but it will be worth it in the long run.
The no shows - Do you have a thorough prescreening on the phone or by email? Ask all the hard questions and weed people out before investing your time in an appointment. You are obviously a very busy woman and your time is valuable. Also, do you actually call yourself a 'sitter'? Or are you a home daycare provider? Because there is a world of difference. We home daycare providers have contracts, schedules, and because we are self-employed we are businesswomen who make the rules for our services. Are these people realizing that you are not confident in your abilities and your business? Take a hard look at all of that.
I have 2 pages that are the legal part of the contract and 6 pages of policies and I make the parents initial every paragraph to show me that they have read it and 2 pages of medical information in case of emergency and that's all I have. I like to keep things simple and uncomplicated because I believe the parents will remember if there is LESS to remember. I would be happy to email my contract to you if you pm your email to me. Always happy to help someone new because I was in your shoes when I started.
Lastly, there are so many problems that I didn't even address that I saw in your post. But it all boils down to this - TAKE CHARGE OF ALL OF IT, NOW!!!