I successfully restructured my hours and tuition after my first child was enrolled. First the new policies were rolled out to all new families and
eventually notice was given to that initial family.
One thing to be clear on is
what is the goal with the change.... my end goal was to shorten my day with the changes, it sounds like your goal is to increase income so always keep that in mind. I bring this up for two reasons 1) I always knew when I opened I wanted a short day but my policies did not match that - they maximized my income with the potential of a shorter day but did not guarantee the short day I desired and 2) because on one hand you state you want $20 more per week per spot but then you also say you want to add a yoga class with an instructor. Having the instructor would increase your overhead so you need to factor that when adjusting your prices to ensure you bring home what you need/want.
A couple different options to increase rates from those already enrolled:
-
Add an activity fee. Sell them on new/upgraded services (preschool curric., music class, yoga, etc.). Tell them the additional fee is X per week and is due regardless of attendance. Really play up the new service(s) and get their buy in. (When I first opened I had a monthly music class fee.... it was required and not one parent questioned this.)
- In my opinion in terms of increasing income the best option is to
switch to contracted hours based on pick up times for all families! When I first opened I offered contracted hours based on pick up times, the first family enrolled needed my max hours so I did not get the short day I desired but I did make a lot more money for my time. With the contracted hours I made $10 more per day than the highest provider in my area for my max hours. BlackCat & DayCare both offer contracted hours based on pick up times so look at their post especially for examples.
Originally Posted by Blackcat31:
I use contracted hours and can no longer wrap my head around why some providers do not. lol!
However, I usually introduce new families to new payment/rate policies but wanted all my families on contracted hours so I could have better control in when I work and when I am off work. I own a separate child care house so I certainly didn't want to be at work any earlier or longer than I really needed to be...kwim?
I wrote a letter telling parents that rather than raise rates across the board, I was instead implementing a rate structure that would allow the parent to control their child care costs. Basically, I "sold" it to them something that benefited THEM. 
Now I know EXACTLY when I need to be here and when I can leave. Thus allowing me to schedule appointments and other personal things outside of work verses having to find a substitute or having to close.
I now make MORE money and work LESS hours.
People will find a way to do X if it will save them money.
If they just pay by the day, then they want their money's worth and won't waste using it.
I think it's the secret to "marketing" and sales really...... 
Full disclosure I opted to do away with contracted hours for myself since I quickly realized I did not want to offer a full day program regardless of the additional money.