Hi Debra,
First of all, your portraits are fresh and beautiful! Second of all, I'm worn out just reading about your week! Whew! You have A LOT of energy.
I agree wholeheartedly with the previous posts about you raising your prices. Here is my example: I participated in a 'show' at a friend's home last fall, I sold little oil paintings of fruit and flowers for $350 (for the 8x10's) and $500 (for the 11x14's). They were framed. But YOU are painting somebody's child or pet, which is about 100 times more valuable to a client than a few lemons from the local grocery store, which is, by the way, why I aspire to painting portraits. I'm not saying you should raise your prices 100 fold

but certainly they should be doulbe what you are getting, at the minimum. In my opinion.
I've had some experience delivering finished advertising and design products to clients. I had a few that wanted things on a 'rush' schedule and I always charged them 50% more. I'm just afraid that if you get yourself into delivering something the very next day, you'll stress yourself out. It would stress me out anyway. I'm just afraid you may have some emergency or personal thing that you need to take care of and there you are, with a portrait promised the very next day. You could always offer the next day service but at a premium. Just a thought.
I think if you keep offering your small fresh portraits, even at twice the price, they will still sell like 'hot cakes'. The clients will find you. And . . . . . just had another thought. Think about how much an 8x10 professional photograph costs! Here in Houston the sitting fee alone is $150-$200, then another $200-$250 for the actual photograph. I'll bet in most cities you can't even get a professional photo done for $200, unless you count Sears. No wonder you're selling those portraits like hot cakes. Have I convinced you yet?
Good luck,
Joan