Allison did an awesome job of explaining here - thanks!

Since I am a natural born list maker, here's a handy list for you:
1. order the economy package (you do the reading)
2. order the science add-on (your child does the reading)
3. order either the Level 2/3 Drawn into the Heart of Reading package, OR the Level 4/5 Drawn into the Heart of Reading package, and EITHER order a DITHOR book pack for your ds to use with DITHOR, or put your own books together (your son does the reading)
4. order 2 semesters of math, an A and a B (both the textbooks and workbooks)
5. order a grammar
6. decide if you'd like the music CD (this was very helpful for my ds to memorize his Scripture, but it's optional)
7. order the Basic package (you do the reading)
8. order either the Deluxe package (if your child is ages 8-10), OR order the Extension package (if your child is 11-12) (your son does the reading) Optional - but excellent to have
I hope that helps!

Just remember that the books your ds reads are scheduled to be read slowly over time. The readings assigned are not overwhelming, but we found them to be just the right size.
In Christ,
Julie