For us we did STOW vol1 in 5 months, but we spent the first half of the year just watching documentaries about Egypt and learning as much as we could. When we started our history in January we would go through a couple chapters a day. My son still remembers the things we learned about in vol1. We are doing SOTW vol2 this year and I expect we will be done by christmas. My son loves history. We do the coloring page and map work for each chapter and use the tests as our review. And we will do a few of the activities but they usually require "things around the house" and I never have those things, we are spending the little extra money we have on our science experiments which in our opinion are more fun. We follow the SOTW for our sit down schooling, but we do a lot of interest led learning on our own as well.
In these early years I think that a love of learning and love for the subjects they learn is the most important part of it. I don't think you should rush through a part of history he enjoys to keep on schedule. There is plenty of time to learn this stuff but only a short time to show them how much fun it can be. As long as it is fun I think that it is certainly doable. If it were me trying to do this I would look at it like semesters Aug-Dec vol1 and Jan-May vol2. Each chapter in Vol 2 takes us about 45 mins (vol 1 was about 30) depending on how many times the younger ones interrupt.
whatever you choose I hope that you both enjoy it!