I use SOTW for my almost 10yo and my almost 8yo together. You shouldn't need to supplement - especially if you have the activity guide. I find the 10yo asks more questions that get us off into further study, but it's plenty. I have the Kingfisher encyclopedia on hand for more review if needed and I usually have books from the library on topic to supplement with.

I don't like the meeting book for everyday use...my ds would get bored with the same questions over and over again. I use it when it is introducing a new concept, but it's not something I fool with too often. Could be because ds had a good grasp on graphs and dates before we started Saxon 2, but I just feel it's too repetitive for us. :)

Barnes and Noble has an Educator card that gives you a 10% discount everyday with 20% off during their Educator Days (going on now actually). They have the application on their site and you can bring it in to any store to receive your card.

I used Abeka3 last year with my daughter but switched to Rod & Staff this year. R&S is more of a writing and grammar book, where the Abeka is grammar centered. If you have the Abeka already, I'd just do that and start on R&S 4 next year. We didn't have any trouble making the transition. I will say that I have to help her alot more with the R&S because it covers a lot of diagramming sentences which she hadn't done previously. Each lesson has a well laid out explanation of the topic which is nice for independent learners. Check out their site, and you can see actual pages out of the books. They review quite a bit, so you should be fine if you do Abeka this year.