I don't recommend rushing with a pre-schooler.
We are getting "serious" this year--b/c we choose to and also b/c we are now entering the compulsary attendance age in our state.
Kindergarten I had formal stuff--but we didn't finish and I am cool with that and DD is excelling anyway.
For pre-school...you may wish to have things for your daughter to do like workbooks and such if she indicates a desire to do this. I will have workbooks for my youngest otherwise she would be bored out of her mind while her big sister does school. She wants to be just like her.
Children metamorphisize and for you youngest--I think it is too early to begin purchasing items for K or 1st grade. You may change your mind a hundred times by then.
Spend this time to research and observe your daughter's learning style and then make decisions based on that.
We have elected to go the classical approach. I want a well rounded child with a "well-trained mind" (a book that you can read if you like). You can google classical homeschooling for more information on what that entails. But let's just say in 1st grade she will be learning about ancient history!
Rainbow Resource
http://www.rainbowresource.com/index.php is a good start for materials. Go to the website or give them a call and order a catalogue and just read and read and read it.
If you have a homeschool convention in your state--you may wish to check that out.
Homeschooling can be cheap, but for most it is an expense not to ignore.
We do a co-op (costs us money) as well as dance lessons and soccer. If you were to do an art class or other music lessons--those will cost money. I use physical activities we already do for PE so I will never do a PE curriculum (and it is not required in my state anyway).
I buy my materials piece meal. I just don't like curriculums in a box. This year it will be about $400 or so just in curriculum. We are still beginners so I have to buy some one time purchase items that I will not need to repurchase when the youngest is ready for them.
Some have done coursework completely free (or very minimal costs) on line and get all their books at the library.
There are a tone of curriculum websites.
JUst begin googling and explore:
key words:
homeschool
curriculum
homeschool curriculum
classical education
teacher resources
homeschool resources
(just think of any and all words having to do with education and you will find so many links).
With your oldest--I don't have any suggestions as I don't have a kid of that age just yet.
With your youngest--enjoy her company and explore the world for the next 2 years and READ to her often. Instead of planning how to fill her days--enjoy the days and use that planning time to research how you will pursue her Kindergarten and/or First grade years.