Welcome to HOD. We are doing Bigger this year and will begin unit 9 next week. We are enjoying it.
I will try to get you started with a list of books. To get you through the first 3 weeks, you will need:
Bigger guide
A First Book in American History
Journeys in Time
Hymns for a Kid's Heart
Cheerful Cursive
Preparing to Build
Storytime Book-Biography (will last 4 weeks) you read to child
One Small Square:Seashore (will last 4 weeks)
Math (whatever program you choose to use)
Reading - follow Emerging Reader Schedule or Drawn Into the Heart of Reading 2/3 - the student reads
There is a list of the emerging readers on the HOD website. The first book is a choice of either The Early Reader's Bible or the Beginner's Bible. If you are using DITHOR 2/3, the first book is a biography
I understand you are spreading the cost, but I would recommend at least getting the Economy Package which includes the guide and the history books. By unit 6 you will be needing Stories of Great Americans, so unless you are getting them used, it benefits to buy the package from HOD. There is a discount if you get the package. You could spread the science out, because that stays with the same book until finished and doesn't mix reading from the different books like the history.
Hopefully that covers each area. If you have any other questions, feel free to ask.